Go to Ian in the UK. He is the go to guy.
I will warn you though, the new ultimate model which is blue has a high level of built in inertia or momentum and you cant turn it off. I have many IBU2s and two Ultimates and I dont use them because they are un controlable in my opinion. They suck for short. Especially if you IR battle. Ive been waiting for a few years for the MFR in Italy to write new firmware for them and he hasnt, I think he wont and IMHO he ruined an excellent product with this inertia thing you cant turn off. So I have scrounged old ones where I can even smoked ones and sent them for repair.... Once I run out, I may not build any more tanks as I dont like the tamiya or clark systems.