Exoterra will work if you have 1 small clutch of BP it's you have more than one or a big one you will be out of luck (a 6 quarts tub does not fit in there), I would also not trust the thermostat and use a external one such as herpstat (in other word lots of money for nothing)

Either build your own it only take a few hours to put together if you use a large one (Old fridge, reliable thermostat and heat tape)

If you want to make a small one a cooler ($15 to $50) a reliable t-stat, some heat tape or heat cable is all you need. I recently put one together in 15 min so I could put my hognose clutch in.

Or buy one that you can grow into no need to spend $100 on something you can only use once, you are better off investing in something solid that will last for years to come and fit your growing needs.

The important thing to keep in mind is that the thermostat is the single most important and expensive piece of equipment you need, the rest is fairly cheap and sometimes free.