I donīt know any pay per sign-up sponsor but here are some russian partnership sponsors:
RussianScan 50% partnership and lots of free content.
Red Teen (SawCash) 50% partnership and free content.
Russian Brothel 60% partnership.
Russian Housewives 50% partnership.
Russian Amateurs 50% partnership with some bonuses, this one uses GloBill, the rest uses IBill.
RussianScan and Red Teen has worked very good for me, the rest Iīve had little or no sucess with.