Hi,
You can really find good cases here:
http://www.skbcases.com
and also here:
http://www.gatorindustrialcases.com (see utility)
They are not exactly for RC transmitter but they have a huge selection of cases, maybe you can adapt one by modifying the foam interior.

I use a SKB golf case to carry my pylon planes. The quality is really good.
-Juan