I got a used tank on craigslist, got glass baffles at my local glass shop and did a DIY sump myself. (pretty inexpensive) If you go on Youtube there are several videos on how to do this. For your tank, I would buy a 40 breeder and custom build it. It's very easy to do...good luck
My neighbor has what looks to be 40b sitting in his driveway. I think he may be trashing it. I'll walk up and ask him about it. Maybe it holds water and is free!