Haha cheers! Nothing too elaborate though, I'm not in any way technically skilled enough to make nice things on my own haha.

And yeah they were RC tank gearboxes, I believe they were 1:16th scale and these ones have nylon gears which are a lot lighter than the steel ones you can get I'd imagine. Which you'd almost definitely need because they're like 200g a piece with the nylon gears! 99% sure you can find roughly similar ones on eBay, think they have slightly different ratios depending on the tank they were used in. Not too badly priced either, not a whole lot more than a pair of the 1000rpm gearmotors from what I've seen.