Cheap way:

Talk to blitzkrieg65 about the DBC (HL radio) or DBCRC2 (hobby radio).

Or YHR about the DBCRC3 if you have a hobby radio and want better sounds.

Expensive way:
Tamiya electronics: check Jason's store on ebay- a reliable source
El-Mod: talk to blitzkrieg65

Hope this helps?
Mart