Re: Mircorp
Personally, i'd go through Energiya or Rosaviakosmos (after all: these are the ones who ultimately will bank your check & make the final choice yea or nay); but if you still feel the need to use middle men, Space Adventures can still get the Russians to answer telephone calls. Given that you would competing with officially sponsored astronauts from Europe & elsewhere for your seat, though, a better bet still would be to push the idea through your local national space agency; & let the deal be struck on an intergovernmental level... less bs; & more reliability.
Robert