Guess we don't have sail bags.., strange. We have sails that come with bags, but no bags.
Best bet would be to go to a local canvas shop, give them the length and how much diameter and they should be able to knock something out pretty quick and easy.., and fairly cheap. Sailmakers hate to make bags for the sails they make and really detest making a bag for someone else's sail.
My tramp gave no signs of wear, but this year at Bay Week on the first day both sides ripped out. I had to jump from hull to hull to tack or jibe.
That cost me big time -- sprained my back and was out for a month
Good luck,
Rick