My understanding is that the vacuum ports on the pump are for the wipers. Mine are not working, so I can't say for sure.
I bought a pump on ebay a few months back for about $40. It has the two vacuum ports on it, but are not yet hooked up.
The part # for the one I got is Amoco 3461. It is NOS, so as John said, there's no telling how long it may last.
Do you have one, or two ports?
If you don't have vacuum operated wipers anymore, then 390 mechanical pumps are easy to find.
You might want to consider an electrical pump also.