Another possible option is to use companies such as Shaeffer AG. These guys are based in Germany but there is a counterpart in the US. They have their roots in building front panels but extended their business to complete housings and even tooling. The company provides the design software for free.
I have used them several times in the past, mainly for front panels. I guess someone needs to create the design for a wall mount and then either make the design available though this forum or organise a “bulk purchase” for people who are interested. The later option would bring the unit price down a bit.

http://www.schaeffer-ag.de/en/produk...ine-parts.html