You could also check with a sign shop. Most shops carry matte banner material and if you're lucky, fabric banner. This is a very cheap option as well (I know because I worked in the sign industry for quite awhile.) You should be able to get a small sample done for free prior to actually ordering the size you need. I would HIGHLY recommend getting that sample if you decide to go this route because some sign shops think printers never need to be color or feed calibrated (dumb.)
If you are able to find a shop that has fabric banner in stock, ask them for a small, solid green sample on matte AND fabric banner material as you'll be able to tell if the printer is capable of producing the color you are wanting and if there is any banding in the print. It will be a lot harder to tell these problems if you just have them print straight to fabric until it's too late (like during post.)
I recommend this route because most sign shops stock banner material in widths between 60" - 120" x 30-50 yds. long. Sign shops can also install grommets along the edges so you can cheaply hang your green screen with bungee straps or rope.
Interesting idea!! I like the idea with grommets, etc too...would make it easy to mount about anywhere I needed or wanted to...
I do need something pretty wide as that the first thing I'm thinking about was filming some boots walking across the screen, then torso in a poncho to a reveal of a Clint Eastwood type thing in his old spaghetti westerns...wanting to do this and put an old western desert type background in there....so, I need something wide enough to walk across a few steps.