A while back there was plenty of advice about fitting a 2G4 module to replace the original sets RF unit. I got the feeling that it was only applicable to certain radios. Obviously, a new, compatible, receiver was needed. No idea if the units are still available.
The link above is to a thread from 2012 – looking for the module used back then shows that the particular item is discontinued. A search for "2G4 transmitter conversion module" gave **LINK** among other clues. Again, they usually only work with the same brand receiver.