I don't know much(almost nothing) about pollenation requirements for stonefruts.
Would P.angustifolia(native Chickasaw plum) work? If so, I think Just Fruits & Exotics, down there in Crawfordville, carries the 'Guthrie' selection - it's a good one, and adapted to your region. They may also have some other varieties that will perform.

I've had some beach plums growing here in KY for about 115 years. Hope you don't find yourself as disappointed as I've been - fruits are very small, with minimal 'meat'; quite tart and flavorful, just not much there. Granted, mine are just seedlings, but I suspect their performance is typical of the species, when grown in my locale.

Emerald Sea, looks like this very unique native plum to the Northeastern shore (Cape Cod), doesn't need a cross pollinator. It is suggested to get two Beach plums to improve pollination. That way, there's no issue with timing of blooms for cross pollination. Neat plum, and Cornell is running an entire project around the Beach Plum, so you might want to contact them if you're really wanting a different variety to use for cross pollination.

Patty S.

Here is a link that might be useful: Cornell Extension: Beach Plum Project

Oops. 115 years? Not quite. Fifteen.
I don't know how those 'northern' plums are gonna do down South, with regard to chill-requirement, etc.

Got mine from OIKOS Tree Crops years ago. Seedling selections, but relatively inexpensive.

Here is a link that might be useful: OIKOS Tree Crops

Thanks to both of you for your kind responses, and especially the links. I do hope the tree will manage without extended cold in the winter. It appears to love the sandy soil around here, at least.

I plan to ask the two nurseries for possible options, but perhaps to be on the safe side I'll add a second Beach Plum... they don't seem to grow too big. It's interesting Cornell has a whole project around them.