I have been very pleased with the selection and prices at Bluestone Perennials (bluestoneperennials.com). It is late in the season, so availability may be limited now (but everything seems to be on sale too). Good luck!

Most of the ornamental grasses can be grown from seed (they are, after all, grass). It's obviously a bit late to try at this point but next year consider this approach.

Last year, North Botanical Gardens had a nice end-of-summer sale, where it was a buy 2, get one free on certain types of ornamental grasses. Of course, that does not mean they will do that this year. But in general, if you wait until the end of august and into September sales, you can get good prices on grasses. The Phantom Gardener also had some good fall sales, with 50 - 75% off on grasses. Granted, your choice at the end of the season is not always the best, but when some of the grasses have done with the seedheads, and pretty much look dead in the containers, you can get them quite cheap ! Last year, I just stuck about 5 small containers into my mulch heap, and they lasted fine through the winter.

Also, if I buy a large container (say a 2 gal), I cut it into 2 or 3 plants - grasses are super hardy for the most part.