Homemade banner frame
A Google search (which you can do also) found this site:
http://worthingsigns.co.uk/OUTDOOR-BANNER-STANDS.html
Looks like it could be made of PVC also.
Just an idea I did in the past, you might consider making one from chain-link fence components available at HD. They sell the the galv. pipe and corner pieces, I believe the pipe is 10' long, you could cut to fit and then put the four corners on and make the frame whatever size you want. Use bungee cards to secure the banner to the metal frame, the ones with balls on the ends they use for canopies, they will keep the banner taught and free from sagging.
If you don't like the look of the galvanized metal, you could paint the frame or sleeve it with cheap thin wall white PVC pipe, before putting the corners on the pipe sections. When I used the thin wall PVC pipe to cover the metal pipe, I didn't like the imprinted wording on the plastic pipe, so I used some type of solvent based cleaner to remove the text off of the PVC pipe, can't remember what I used, I tried several before I found a cleaner that would remove the text and NOT melt the PVC pipe. Oh, I did paint the four corner pieces white to match the white PVC pipe.
Any, it worked for me.