Just to amplify what Terry said...
What the dealer told you was total BS. One of the great joys of having multiple Totos is the fact that the replaceable parts are completely-standard and available anywhere.
And the real key is this. Korky (Lavelle Industries) makes many of the original equipment parts for Toto, as well as the exact same parts under its own brand name that you can get anywhere. Korky is the inventor, decades and decades ago, of the flapper. It makes everything right here in the U.S., in Wisconsin. They have videos online of how to replace any Korky part, and have excellent, easy directions. Their stuff is available at all the major online sources (e.g. that big consumer site), as well as HD and Lowe's, and your local hardware store. The Korky MaxPerformance Platinum fill valve, model 528MP, will fit any Toto toilet (other than the in-wall tank ones and the $4000 washlet toilets). Terry carries the Pro version of this valve (largely identical) on his truck. One fill valve for all Toto (and most other gravity-design) toilets. Pretty slick. Toto also sells this same valve under its own brand as TSU99A.X, the Toto Universal Replacement Fill Valve. Different Toto toilet designs have different "refill ratios", which is the percentage of the water going through the valve that goes into the bowl instead of the tank (i.e. down the overflow riser in that little hose that we all are familiar with). Because of this, the 528MP has a little knob you adjust to get the bowl refill just right. Replacing the valve takes less than 5 minutes once you have done it once. And it usually doesn't need to be replaced, because all the water-sealing-and-moving parts are in a little cap that screws into the top of the valve (R528 cap), and costs $3. When the seal goes in 5-10 years, you spend three dollars and 3 minutes and replace the cap with no tools required. It doesn't get any easier. The 528MP costs more or less $10, depending on where you get it. Fluidmaster makes a version of its fill valve that also has an adjustable refill and fits right in. (Disclosure: Toto uses a few different fill valves as factory equipment in the delivered toilets, including one of its own design, but it has just one replacement valve, the Korky, which fits all their toilets. So if/when the valve goes bad, you might need to swap what's in there for a Korky, but that's the last time you should have to swap the actual valve rather than the $3 cap.)
As to the flapper on any 1.6gpf or 1.28gpf Toto, any standard 3" flapper will work. Korky makes a Universal Toto Flapper that you just turn a little band on to get the right amount of water to drain from your tank. It can be had for like $13. Korky also makes individual flappers for different models for a couple bucks less. The 2021BP, for example, fits a wide range of Totos. It can be had for like $9. (Any 3" flapper will "fit"; you just want to get the one that closes at the right time so you don't waste water.)
If you get the 1G model (the one-gallon-per-flush model -- CUFG instead of CEFG in the model number suffix) of the Ultramax or the Drake II, it has a more complex flush valve, because it has to measure the water more precisely, like down to the tablespoon, to get the maximum effectiveness of the 1G flush. But the only thing on the 1G flush valve that wears out is a relatively-inexpensive rubber seal, so under normal circumstances it's not a big deal effortwise or moneywise to change out. Still, unless you have a real need or desire for the 1G flush, we recommend the 1.28gpf versions.
The whole point of Toto is quality, quality, quality. As Terry points out, Toto doesn't cut corners on little stuff to save a few pennies. It's an absolute disgrace that any toilet manufacturer would give you anything other than brass bolts to go inside the toilet, because brass bolts don't rust. We have pictures on here occasionally by folks wondering what that brown stuff is around the holes in their rims, and what is streaking down their toilet bowl in their couple-year-old toilet that worked fine until now. It's rust, guys. Rust from the toilet tank bolts that aren't brass. Rust that didn't appear for a while in large quantities, which unless you really thought about it you wouldn't blame on the manufacturer. But it's entirely their fault. The tank-to-bowl bolt set is a big bugaboo among several of our professional plumber members, whose goal is to install the toilet on the first trip with no leaks, and never get an angry callback from the customer. One member, for example, just throws away the tank bolts that come with the toilet if they are not brass, and installs a professional grade brass bolt set that is never going to leak and never going to rust. You don't have to do that with a Toto, because that's what it comes with.
We have one old toilet (that doesn't get used much) from Standard (before it was American Standard). The manufacture date in the tank is 1927. Guess what material Standard used for bolts in 1927? Right. Back then, they of course only used brass. Almost 90 years later, no rust. The same thing will be true for your Toto if it is left in place for that long.
Dealers get rewarded for moving certain quantities of certain brands, as do their employees. The length and detail of this post is precisely because I despise how these little liars will try to make a sale by saying some stupid, untrue thing that just sways a customer enough to buy the crappy product the dealer is pushing. The only way to counter a claim like, "It doesn't use good parts." or "Parts are hard to find" is to lay out what the parts are, where they are from, and how much they cost.
[By the way, Kohler is the brand that insists on using proprietary parts, including things like weird-design flappers or flappers in sizes like 3.25", which nobody else makes. It's pure hubris, because the designs make no meaningful difference in performance, but do, I imagine, keep the replacement part profit high.]
