My "panties" weren't in a bunch.
I have done quite a few bag
signs over the years made from everything from oilcloth to 16oz. material. We used to hand paint them and then along came computers and vinyl plotters and painting (aside from a stroke here and there) faded away.
I had no idea the OP was looking for POLYbag
signs. It never occurred to me that the OP was looking for those as there was no mention of either "poly" nor political campaign. With no reference to the frame of mind, then as a
sign maker a "bag"
sign is something I hang on a pylon
sign which advertises the new tenant/owner.