I've only been able to find used 20 gallon oem straps.
When I had a strap end break, I removed what was left of the threaded section with a grinder, beveled the end, and welded a new threaded section (from a bolt) on to replace what broke off. Worked great.
Remove the tank from the shell, clean out all the mud and clean off the rubber sheets (power washer works great) and make the drain holes bigger and add more. Paint the inside of the shell too.
Find the crack (probably at the top from the strap being over tightened) and use a hot iron like a soider tip to swirl and plastic weld the crack back. Then scuff up the area and coat with epoxy to further seal it. Online boating places or marine store should have what you need
1975 CJ-6 304 T15 Dana20 30/44 3.73
1983 CJ-8 258 T5 300 30/44 3.31 Looking for full or half hardtop buy or trade
1986 CJ-7 Laredo 4.6 stroker T5 300 30/44 3.31
1986 TJ-7 Trail Jeep project in the works
2003 Inca Gold TJ Rubicon