I have been replacing my boards, also. I haven't been to look yet, but was told that Home Depot sold the large sheets of whatever those sheets are made of and you could cut a lot of them from one sheet. Also, the sign shops have them. Need to check into it further. I also was told that when fabric stayed on the bolts a good while, the dark could transfer to your fabric. Haven't seen that happen, but did see it happen with a table cloth I had my good cloth attached to.
Peg-TX
Innova 18"