1. You can try B4 or Team Losi.
2. If you can't find from e-bay, you can replace the rear hub by Tamiya's one (e.g. TA01/2, DF01) and use the Tamiya 70mm 狗骨 or 萬向狗骨. You need to drill the hole of the rear hub to make it a bit bigger to suit the British Unit.