You could try
GTR Shop . Matt will ship to the states as they have before.
Why would you want to put a single turbo on an RB26? It sounds like you are not exactly falling out of pocket with cash. That is for one a VERY expensive idea since you would be looking a HUGE money to strenghten up the internals and do the head.
You can make just over 600hp easy with low mount turbos on the factory manifold and standard motor. It probably wouldn't last too long but you can do it.