We tried Sugar Lace II a couple of years ago and trialed it against all the tall ones we could find locally and liked it better than all the rest- and it has no strings!
In our garden it reached about 3' but I think it's supposed to be shorter than that (20-24"?). They say you don't need to give it a trellis but we give it support anyway. I've only gotten untreated seed- not sure who might sell it treated.