These should be available by mail order. You don't need to start with 1 gallon plants with Pennisetum. They will fill out quickly. A search on Goolge brings up a first page with the following suppliers:

Santa Rosa Gardens
Nature Hills
Wayside Gardening
Bluestem

If all you can find locally is larger pots, you can divide the clumps into four pieces and plant them. Now is the time to do that since they're a warm season grass.

Or wait until later in the season when they go on clearance, the small pots transplant better anyway.

Thank you so much for your advice. I will definitely look into these options.

Has anyone grown, Pennistenum, Cassian? Its very pretty and I'm wondering if its hardy.

Pennisetum alopecuroides 'Cassian' is hardier than the species in general. I believe it is hardy in zone 5. Maybe even colder? I'm not sure about zone 4. Maybe someone here can verify.

It's not as small as 'Little Bunny' for sure and just a bit bigger than 'Hameln', but still compact, about 2 to 3' tall. It's a nice selection.

Did you try Bluestone perennials?