Instead of specialised (read expensive) in-wall speakers why not cut a hole, make a neat frame and a small internal shelf/mount

I have a pair of Acoustic Energy AEGO 2 speakers

They are tiny - 4" high, 3" wide, 3" deep
The case is metal and they're very nice speakers. I love the sound they make!

They come with a surround box (which you probably won't need) and sound really really good. Personally I'd look for some 2nd hand on ebay