I designed my dark cloth out of black velveteen, and a white nylon outer lining to reflect sunlight. At one end it is folded over and sewn so you can thread a piece of cord or twine through it to secure it to the camera, or at least draw it together. The velveteen traps light very well, and it also adds some friction to the cloth so it won't slide off my camera if I don't want to tie the string. The nylon is a little bit shiney and keeps me cool under the cloth. An added bonus is that the shiney white nylon makes a great reflector in a pinch. Best of all, the materials were only about $20.