[Propane tank replacement for 1986 Toyota Dolphin]

I found the following markings on the tank:  Sherwood 3329 S12;  Helco model 50

[Propane tank replacement for 1986 Toyota Dolphin]

I've heard that they don't make this type of propane tank anymore.  My worry is that mine might break and I won't be able to replace it.  And if it breaks I won't have any heating and can't use my gas stove.  So I might not be able to use my RV very long.  Does anyone have any suggestions on how I can mitigate this problem?  Otherwise I might sell my RV even though I recently bought it.  Thanks for any help or ideas on how I can get a tank replacement.