Grows on You is a friendly forum for gardeners to ask and answer questions, show off our triumphs, commiserate about our frustrations, and otherwise have more fun with gardening.
Sadly, for your purposes, we don't sell plants, though some of our members can probably give you pointers on how to find what you need. I myself would probably have to do what you are doing--searching for nurseries that sell Thunbergia mysorensis.

We don't ship anything as we don't sell anything - this is simply a forum for gardeners to share information, ask gardening-related questions, and chat. :)

The section that calls itself a garden centre on this site just has suggestions for suppliers, not sales, as the others have said.
I just googled it adding USA to the plant name and found several suppliers.

Try
http://www.zone9tropicals.com/index.php