Welcome to the board
Quite the find for such a low hour boat.
Wing Inflatable in Arcata CA would be worth contacting for a price. They make a lot of the government tubes, and use a different yet very tough material. Luxury RIBs in FL is another one, and I am sure there are other tube makers around. Easiest if they already have a pattern.
If the condition of the tubing material is in good shape, you could take them apart and reglue them. A 5 gallon bucket of Stabond 2 part glue runs around $800.