When I bred Colubrids, I built a simple cheap incubator.

Polystyrene Cooler Box, Plate of 8mm Glass, Fish tank Heater, 2 Bricks, Thermostat.

Methodology: Place 2 Bricks either end on bottom of Cooler Box, Cut Plate Glass slightly smaller than measurements of Cooler Box,
place Plate Glass on Bricks after submerging Fish Tank Heater on bottom, fill with water to just touching bottom of Plate Glass.
Attach thermostat, set temps, switch on Fish tank Heater. I used a Fish tank Heater that had an adjustable temperature.
It worked well, you just need to use the size of Cooler Box in ratio to the size and quantity of tubs you are going to put in it.
Would work for breeding one pair of ball Pythons.

I managed to maintain temps between 30 and 32 Centigrade with no problem.
I hatched King Snake, Corn Snake, Rat Snake, Childrens Python, African House Snake, Herald Snake, Night Adder, Beardie and Gecko eggs in it.
I don't see why it would not work for Ball Pythons.