Personally,ive never heard anything good about exoterras. Before i lucked out and got a mini fridge inc, i was gonna use a hovabator and remove the built in wafer t-stat they come with and add my own. Another cheap(but iffy) suggestion, since time is short you could get a small cooler...add water and an aquarium heater and small shelf to place inside to hold egg tub. The aquarium heater will heat the water and inside of the tub creating an incubator.

To have mom incubate, even though shes doing the work...YOU have to make sure you provide her with the correct conditions and materials for a solid two months for her to properly incubate.

P.S.- These are just suggestions, im a first year breeder myself. Im just replating info ive come across here n there. Rich is MUCH more experienced.