You'd be looking at a standard US 260 gallon tank. These are not cheap to buy nor to build for yourself. And that's not even including the stand. $900 to $1,500 USD is the lower range for a used tank & stand that I've seen on forums & CraigsList. I shudder to think of the retail price plus shipping & handling.
Have you considered MacGyver'ing a humidity dome or perhaps using a simple humidifier? It'd take up a lot less space and be way cheaper. Amazon has humidity tents for $30 to $75, or however much you wanna spend.