It's impossible to buy new tubes or anything for repairing tubes, here in the Bahamas. My rope bolts separated from the tubes along both sides, recently. A DIY job was the only solution so, with the aid of friends in the US., obtained four tins of 2-part adhesive (Poly Marine - made in Wales) and set to work re-glueing everything back. I think the cost in the UK is about £13-14 per tin + catalyst; $50 (£34) in the US (West Marine) and, with shipping and duty, landed in Bahamas - $100 (£68) per 200 ml tin!! Total cost: around £400 just for the adhesive, plus my sweat to install it!
There aren't too many RIBs in these pristine and beautiful waters (except those that are carried as tenders on the super-yachts), hence, one has to be pretty dedicated to the cause (or stoopid) to own one...