While we do not currently make custom-install products, it is definitely a future option.
The Alternative
For those with limited floor space, our non-tower speakers can all be flush mounted to a wall via our brackets.
Just make sure and use two brackets for our larger, reference 1723 Monitor and Center. Furthermore, we always insist on mounting our speakers flush to a flat surface.
Recommendations
If you are limited to In-Wall/In-Ceiling applications it is important to choose speakers that follow a similar design philosophy as our speakers. You want a balanced sound with very good directivity control, which means good on and off-axis response. It is also recommended to have a good room correction/EQ to compensate for the installation location and to get them as close in timbre as possible.
Companies, we and our customers had good experiences with are: