Hello, I spent quite awhile online researching exactly what type of pipevine the Pipevine swallowtail utilizes for the larval stage and where to obtain the plants. The best source price-wise of Aristolochia tomentosa (woolly Dutchman's pipe) is Missouri Wildflower Nursery, www.mowildflowers.net. You can call, email, or FAX in an order. I also found the seeds of A. tomentosa and A. serpentaria on ebay. They require stratification for 90 days.
Be careful which species of Aristolochia you buy. A. tomentosa, A. serpentaria (Virginia snakeroot) and A. durior (Dutchman's pipe) are definitely food sources. The female will lay eggs on some of the others, but the larvae will die.
Missouri Wildflower Nursery is also a fairly inexpensive source of milkweed plants. The smaller ones are $2.25 each.