You should be able to find butcher's twine in the kitchen gadgets aisle at any good-size supermarket. It's really just white cotton string. They also make silicone tie thingies in bright colors that hold their shape however you twist them, but you'd probably have to go to a kitchen specialty store or get them online.
I am just wondering, as feeding the wings and legs through the skin have not worked tonight. I finally ended up just cutting the meat off the chicken and putting the meat alone in a roticerie basket instead of doing the whole chicken the old fashioned way. But I am so disappointed in having to do that. I just could not come up with anything to truss the legs with and they kept getting caught on the burners.