Start looking for a Carter M6902. They've been out of production for awhile. They are the better pump, with a rating of 6 PSI, so no regulator needed. They are clockable, so can be made to fit more easily. They're also rebuildable, so when you find one, it should be your last.
They show up on Ebay occasionally, or consider a "part wanted" ad here.
The down side is they don't look identical. My guess if you were considering buying a modern replacement, it's not that big of a concern.
