From what i gathered about my rc engines they can rev anything up to 50000 rpm i dont have any idea on the airplane engines though.
As for the superchargers i have seen them on the large scale fg cars which run on 2 stroke mix so not sure on them working with nitro ic engines. I have also seen forced induction home made with a pc fan some piping and battery pack which when turned on forced air into the carb of nitro engines, i would assume they take alot of tuning to setup and to be honest i wouldnt have thought it would be worth it as nitro engines get stupid hot and the fuel tanks only last for 15mins. I might be wrong with what i have said above so dont take my word for it.
On the shop front i would sugest using
http://www.benracing.co.uk/ best place i have found for a proper shop but ebay has loads of bits and bobs and if you want to w8 a little on shipping try ebay.com.
Hope that helps a little