We bought Caroma dual-flush toilets about 7 years ago because we were so impressed with them while on vacation in Australia. We've been very pleased. I just looked to check on the rough-in. Most are "10-12" adjustable." A few are 12". They may all be dual-flush.

We bought ours from a local plumbing store, but looking online I see that Amazon carries some. Wherever you are you are likely to find this brand not too far from home.

Here is a link that might be useful: Caroma toilet models

Toto has several - the ones that take their "Unifit" adaptor, American Standard has several in their Cadet 3 and Cadet Pro lines and their low-end Colony FitRight (or is it RightFit? don't remember). Gerber has them in their Avalanche and Viper lines.

Are you in California? If so, good luck getting a 1.6 gpf. I ordered a simple Toto Drake 1.6 in April or May and they delivered a 1.2. When I squawked to my designer, she cited the new rules. I was not happy, because I hadn't gotten a Sanigloss model and had read horror stories about 1.2s and solids.

I'm very happy to report that my modest little Drake 1.2 sans Sanigloss is up to all tasks. :)