WTB (or trade) National Semi MM57126N Shift Register

[d b]

A couple of suggestions for people to contact for a lead on your IC:
Joerg Woerner through his datamath.org site
Victor Toth at his rskey.org

I sent a note to Katie Wasserman and Tony Duell noting your Classified post too, to make sure they see it.

There are more here, but those four came to mind first as encyclopedic in their knowledge of parts & cross overs.

I think that vintagecalculatorsinc on ebay was and maybe still is selling off Guy Ball's thousands-o-calcs. He might have one that he's getting around to selling or even know an affordable parts source, but don't expect a deal.

Good luck. -db