As mentioned a Christmas Tree tub would work, but I would personally pass if you cannot afford an actual cage for her right now (I don't think it's fair to stick her in a tub when she needs a cage IMO - "needs" as in I wouldn't put a adult Dumeril's in a tub if I owned an adult myself).

But, have you looked into building your own cage? Or have someone help you with building one? If you're up to the work you could make a nice cage for her at a LOT cheaper price than buying one. That's my plan for my boas Plan to build our own and just buy the actual RHPs for heating and the thermostats to go with them.