You want Smilax smallii aka Smilax lanceolata. It is thornless and the one commonly grown as an ornamental. The traditional way to acquire it is to ask someone who grows it for a start. Ask any neighbor or stranger; if they have it on their front porch, they are used to sharing.

If you are shy, you will have to buy it. This is difficult because smilax is rare in today's nursery trade. Here are 2 mail order sources: www.mailordernatives.com and www.woodlanders.net.

I live in raleigh and i am looking for smilax too. have you had any luck?