Jewish Russia through Khazar influence?
I think a number of people on this thread think of the Khazar state as being more Jewish than it was. Probably only the ruling elite had converted to Judaism by the 800s. It was a multi confessional state that embraced everything from paganism through Christianity and Islam. Sure, you could get Jewish missionaries in Rus but remembering that from the 9th century the Byzantines were actively trying to convert the Kievan state and both the Rus and the Byzantines were angling to weaken or destroy Khazaria.
Bash the Byzantines for more options.