check with one of your local sign manufacturers. My friend cut mine and wouldn't charge me for them! What a great friend! He said they had the material and it was going to be thrown away if it wasn't used. It's called coroplast. I've seen someone buying them from Polar Notions. When the price was broken down I think they were a $1.00 ea.
I also found bolt buddies from Pals Productions and bought 200 metal clips to hold the fabric to the board. I believe those were 50.00 with shipping. Happy fabric rolling! :lol: