Bud, sit down and think it thru. If your 260 bag is like mine (likely is) you will see that the cloth bag and throat are sewn together to make one piece. Its held onto the bag ring with a metal band. Remove the metal band, use a seam ripper to undo the stitches holding the sateen to the throat and reconstruct a throat using some heavy canvas or vinyl. Someone who knows a little about sewing could help you out. A tailor or seamstress could likely do it for under ten bucks. Then refasten the re-sewn piece onto the bag ring using a nylon tie or some heavy wire.
Working on these old machines sometimes requires thinking "outside the box".
Working on these old machines sometimes requires thinking "outside the box".