If you need a bladdered tank for track requirements you're kinda stuck. Dave has the big 42 in his car. You could go that route for similar money or the same size as you already have here
PhotoPost Classifieds - Leaky Bladder? Tank for CSX framed cars - Powered by PhotoPost Classifieds and save yourself some cash.
Of course this one has an inductive tube solid state sender that almost works right.