I have a 68 Country Sedan, and I went looking for quite a while without finding anything new. I did track down a shop that would repair your existing tank, but I didn't save any links: Just google tank repair and hopefully you can find something useful.
If you can't find a parts car, your only option may be to call a manufacturer like Tanks, Inc. (http://www.tanksinc.com/index.cfm) and ask if they have anything that will work. Phone (877) 596-3842