A couple of comments: FWIW, in MA, even though you may find a toilet in a local store, if you're getting a permit for the install (and technically, you are supposed to, but few do), if it isn't on the MA approved list, it would not pass. So, you might want double-check the MA official website to verify your decision is actually 'legal' to install. Your choices for 10" rough-in toilets is restricted. There are some toilets that have a significant space behind them, so some 12" rough-in toilets may fit. Most of the time, you can fudge the centering of the toilet on the flange and gain maybe 1/4". So, a toilet that normally have 3/4" behind them, with that extra 1/4" you fudge, you might have a larger selection. Also, make sure you are measuring from the wall, not the baseboard.
It's getting harder and harder to find low toilets. The height of a typical dining room chair is 16-18", and many of the new toilets are within that range once the seat is installed. As the population ages, that extra height is appreciated.