For buildings in that scale, check out Japanese Railroad stuff; N is the most popular scale over there, and I got me some pretty cool buildings from there.
Also, check Ali Express, as they have some very affordable flat-packed polystyrene buildings in different scales. I've got a lot of those, for use with 10mm and 15mm armies, and they tend to work with both (if you squeeze your eyes a bit
).
I have the entire not-Transformers line form Botwars, before they stopped doing them in anticipation of the Wizkids minis, and they're pretty small. Indeed roughly 10mm.
From what I hear though, the Wizkids ones might just be slightly larger. but then again, with G1 scales/dimensions all over the place, even in the cartoons, I'm sure they will combine just fine...