I tried parviflora and obovata last year from seed and failed with both. I think they need cold stratification, but not sure for how long.
I have 2 parvifloras in ground that I bought from a local nursery here that sells them as butterfly plants. Got them last spring, they put on decent growth. They are both in shade in a little oak dome that is slightly higher than the rest of the front yard. They get next to no water other than rain since they’ve established, and are currently both dormant. I also have a longifolia/angustifolia.
This is where I got them from, however they don’t ship.
There is also:
But they seem to only have obovata and reticulata atm. I have talked to a couple of local nurseries around here, and sometimes they have them and sometimes they don’t.