I've ordered from Mischel's Greenhouses several times

Annie's Annuals http://www.anniesannuals.com/ has lots of unusual annals and a great reputation. She is a bit pricey. Call her if you plan a very big order and see if she will discount.

The other ways to do it would be use Bluestone http://www.bluestoneperennials.com/b/bp/index.html and buy less expensive perennials that you treat as annuals.

I suggest that you haven't discovered the locally owned garden centers/nurseries in your area. Local sources are able to stock unusual stuff rather than run-of-the-mill, and are also able to use local growers. As a matter of fact, any home town business NEEDS to supply that kind of material, rather than try to compete with the chain stores.

Perhaps, for next year, you can contract someone to grow a few things for you. It doesn't sound like you need very much, but are just looking for something less ordinary.

I agree with rhizo - not to mention that getting good quality, nice sized plants from a catalog/mail order source "without breaking the bank" would be difficult at best. Shipping charges would kill you, and shipping finished annuals without damaging them is unlikely. Keep searching - ask questions and explain what you are trying to do! The plants are there....