Looking for 68851 PMMU

Since some of you seem to know the sources for old/obscure chips... I'm in the process of sorting through various Mac II pieces around here and was considering setting up NetBSD on a spare system. I have one board which already has the FDHD upgrade, but I`d still need to find a 68851 PMMU. (For those who don't know, the 68851 is the Paged Memory Management Unit (PMMU) for the 68020 processor.) Do any of you know of an inexpensive source for one? Or have a spare laying around? I've looked at the usual mac upgrade places and have seen prices of about $50. For that price, I could just upgrade to a IIx. (I already have a spare IIx motherboard, just need to get another ROM SIMM.) I just figured that and FDHD upgrade set was to good to just sit idle... :-) Thanks... <<<John>>>