In 2004, I had
RDS Aluminum in Perry, FL, make a copy of my original 27 gallon tank from my '72 Seafari, but with internal baffles added in. It included sensor, fittings, flanges, and double grounding strap connections. Total cost was $197. Aluminum prices are WAY up, though, from 4 years ago.
Figure on between $13.50 and $18.00 per gallon for a custom/duplicate tank today, not including shipping your old tank to them, and shipping your new tank back to you. But Perry is only 2 hours up the road from Inglis, so you could save a lot of money that way.
Another way to save a little money is to buy a "standard" size tank that will fit into your existing space, such as the RDS tanks at West Marine, or
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Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury