Welcome to the forum! What a nice post! It certainly shows what a difference a lower-flow toilet can make when you have to pay a significant cost to dispose of every drop of water used!
I doubt anyone in Alaska is going to be as responsive as Terry!
I should mention to you that Toto now has a model of Drake II that only uses 1 gallon per flush. In the real world, it seems to be available at a price pretty close to the 1.28 gpf Drake II. However, I would caution that it just came out, it looks somewhat different than the regular Drake II (and hence somewhat different from your Vespin), we haven't heard from anyone who has used it and so don't know for sure that it's a definitive single-flusher (although we have very high expectations), and we notice that instead of the simple, straightforward guts that your Vespin II has, it appears to have a made-for-this-toilet flush valve that you can't just go get a flapper for at Lowe's. In Alaska, I would think that ready parts availability is important. That said, Toto customer service is really quite good at getting parts out the door the same day if there's a problem.
And if you're buying from Terry, I know he is going to take care of you. I don't know if he's sold a 1G yet, and I haven't seen any comments from him about it yet. In your use, reducing water usage per flush by 20% even over a 1.28 might be meaningful, but I don't know that you want to be the guinea pig.