Jairus, the car must be scarce in your area but in SoCal, they are far from rare. Over the years we picked up quite a few for the museum, loose and new in original boxes, in 6 colors. The "hard-top" dune buggy was in production from 1970 through 1977, first from Riggen, then from Gayla Industries, and when Gayla went belly up, REH still had dozens of the cars that they marketed over the years.
The Cox parts are absolutely correct on these cars, as Riggen had purchased lots of guides and crown gears for their JAD 1/24 scale models, and eventually purchased a quantity of leftover motors, TTX100 formerly used in the 1/24 and 1/32 scale Cox kits and RTR, then NASCAR and Super NASCAR "16D". A large proportion of the 100 + MIB 1/32 scale RTR at the museum have these guides, gears or motors. Riggen also used the old gray Revell motors from the huge unsold pile that the Marina Del Rey company was desperately trying to unload in 1968.
The Cox guides and crowns gears ae listed on this flyer: