Tell the nursery the type of plum you want, how many chill hours for your area. And ask them to recommend a pollinator.

Perhaps try: County Offices | UW Extension | College of Agriculture and Natural Resources | University of Wyoming - UW Extension: County Offices.

There is a list: List of Nurseries and Garden Centers in Wyoming - Nurseries & Garden Centers*
in
Wyoming.

Good luck.

There are European plums, Asian plums and hybrid plums. The A. and the E don't cross pollinate. I think hybrid can cross pollinate A.plum.

Please check Fedcoseeds website. https://www.fedcoseeds.com

Their catalog is coming out in Oct. It is a reputable nursery that sell lots of cold hardy fruit trees on top of everything else. A Fedco catalog is worth reading with tons of good info including plum varieties.

Raintree nursery has great grids that show which trees overlap on pollination times.