I'm not sure who carries parts of these HSP things to be honest - if they do at all (someone must, surely). Just take it easy and learn how to control it first and foremost.
You'll probably be shocked if you go to a local club that races off road buggies by the amount of kit everyone has and virtually everyone will have some sort of competition-level car. That said - it's not a scary thing going to a club meeting - you can go along for a look at first and talk to some people and see how it all works. I don't think any club will turn you away because you turn up with a car nobody has heard of - generally people will try and help and you might just get addicted like the rest of us and spend a fortune!
If you don't fancy racing then I can't be much help really but maybe someone has some good ideas?