I have made over 300 purses and I use Craft Fuse or DecorBond for the sides and the plastic canvas for the bottom. All is washable, so if they get wet or if you're spot cleaning it won't disintigrate like cardboard or a paper type product. If you want the sides stiffer, you could use a double layer or you could use a low loft batting along with the interfacing and quilt it. I have used Timtex, but it's harder to work with. guess you could also use Crinolin(sp) as in making hats or really stiff petticoats . When I buy I always use coupons from JoAnns, Hancocks or Hobby Lobby, so the cost is not overwhelming and I buy more than a yard at a time.