Is there anything I can do besides get a new tank?

Here is what do with tanks like this. It's kind of a last resort when a new tank isn't available for a reasonable price. go to the hardware store and get 3000 copper BBs a gallon of 99% isopropyl and a bottle of WD40. I take the tank off, flush it out with some WD40 to get the floating stuff out and then seal it up with tape with the BBs and some fresh WD40 and then shake ever living hell out of it, turning it to make sure get the whole inside of the tank. Drain everything out, and repeat if needed. Just make sure you get all the BBs and then flush it with isopropyl alcohol several times to get the WD out. It can be around $40 or so to get a gallon of alcohol, a bottle of WD and BBs but a new tank will likely be a few hundred dollars. YMMV on this depending on the tank and the severity of the rust, but I've had good pretty luck with it when
haven't had another choice.