My best guess is still the big auction site, but maybe look for a whole Kiev? The B mount is for the old Salyut/Kiev 88, not the 88CM, right? If so the lens should be named Volna. I found about three on the site. If it is indeed the old Kiev mount, make sure not to buy anything maked as for Kiev 88CM/Kiev 60/Pentacon Six.
Anyway, have fun with the Kiev and I hope you have better luck then I had with my first one. (Second one is from ARAX and works like a charm)