7M Willard Tube Set
Back in the day I used to remove & replace these tube sets for the USN. If your successful in finding a replacement tube, I have two (different sized) stainless steel bow attachments and plenty of SS bolts & washers for sale.
If interested can send you pictures.
Best Gene (San Diego)
P.S. You probably know this - Wing Inflatables manufactures a polyurethane version of the Willard sponson - but expensive.