WTB 38-40 gallon tank for sump

[pherbert]

I'm looking for a 38-40 gallon aquarium to turn into a sump to replace the 20 gallon I'm using now. Just two requirements:

1) It has to hold water, 'natch!
2) I really need a tank that's about 36-42 wide x 12 front-to-back x 18ish inches tall.

Anyone have anything about that size they would like to convert to a modest amount of cash?

Thanks