I don't have a lead for you on M. primuloides.

But two other dwarf Mertensias suitable for the rock garden that I grow are M. alpina, and M. lanceolata. These are quite similar to one another as I recall. Small flowers opening pink then turning sky blue. Bluish, fleshy foliage.

I also grow M. maritima.

I agree, choice plants.

Glen, you are growing in a zone 3!! Bravo! Any tips for growing the Mertensia maritima? I hear they can be a bit tricky.
I posted my search in the perennials forum and someone there directed me to the Evermay Nursery site on line.
www.evermaynursery.com
They carry the Mertensia primuloides and some other gems.