Hi Tom:
From my experience, I doubt that you will find exactly what you are looking for. Most BGs are stocked on perhaps 8' or 9' and 12'. I don't think you can find an odd size like 15'. So your choices are to probably work with something that is longer than you want or to cut it down yourself. Not sure if I have ever seen paper seamless rolls much longer than 9 or 10', they are too tricky to transport unless you have a truck.
For painted muslin BGs, I would check with Calumet and Denny Mfg, both are on-line. You should have no trouble in finding a 20 x 20' green screen, also made of muslin or nylon. Walking on a cloth green screen is bad though, once you have smudges and footprints all over it that won't come out, it loses its effectiveness to be keyed easily. For sizes that big, I would prefer a painted hard cyc if you need to see the floor/full length body shots.
Dan
A Producer Who Is Also A DP? Yep, that's Me.
http://www.danbrockett.com
