Last fall I met a local grower who is one of the few in the area with plums.
His favorite is Grenville. I got a couple scions for grafting this spring.
However, in doing a web search I only located a couple nurseries in
Saskatewan who carry it.
This is the description given by this Ontario Nursery
http://www.siloamorchards.com/Plums.htm "Grenville - A cross of the Japanese plum Burbank with native Canadian plum
(Prunus Nigra) from Ottawa 1932. Early bloom, vigorous tree, prolific
yields. Dark rosy red fruit, yellow flesh, large clingstone."