4 cell AA NiCd pack or a spring loaded holder for 4 AA Alkalines was typical.
You'll want to stick with that for CG.
The 72 mhz AM and FM RXs used the same voltage range for about 30 years.
Futaba still sells the spring loaded holder for 4 AAs.
Radio shack sells the same thing but you'd have to attach the plug (cut the lead off a bad servo)