Originally Posted by jrhboxers
You can call sign makers/silk screeners. You can usually pick up their 'mistake' pieces and cancelled orders. I have also gotten them from people who have run for local office and didn't win.
Be careful using "mistakes" and cancelled orders. The inks that screen printers use may be harmful to the fabric.
You should be able to buy a full 4 x 8 sheet of corrugated plastic from a plastic supplier. I own a sign shop and get get the sheets for around $8.00. I don't think I would chance using something that has any type of printing on them.