TinyTreasuresNursery offers plants intended for rock gardens, bonsai and container gardening, and the like. Located in Oregon, this company sells to garden centers but apparently also sells to the general public. Their price list is separate from the plant's pictures so you'll have to surf around a bit to find what you're looking for, but all in all they appear to have a nice variety of items. Go visit their site.
Thanks to Andrew Stenning who contributed the photograph for our masthead