I might have my old mechanical pump laying around.... er, somewhere. I replaced it, but it turned out not to be the source of the problem, so it might still be good. Wouldn't need to charge you but shipping for it... well, actually, since it's well used, it's well smelling of gasoline. Not sure how UPS would like to ship that. Hmm...

It came off my 350/2bbl engine. Honestly - I'm not quite sure where it is! Maybe in the garage somewhere??? I can look around if you need it.

I think a new mechanical pump was only like $25-30 or so at Advance Auto... you might just want to go that route. You'll need the gasket too.