[SilverStreak] replacing 12" round fresh water tank

[<ronda062@xxxxxxx>]

Just purchased a Sabre and she's needing a new fresh water tank; 12" 
diameter (square would work) and 5 feet long.? Any advice on where I 
might locate a replacement tank would be greatly appreciated.? I 
suspect I'll be needing a few more bits and pieces.? Is there a site(s) 
I should try for common items?
I tried searching archives for this info but an error pops up.? 
Thank you!? Ronda