Are you severely set on nice looking cages?
You could store your 40 breeder in your basement away somewhere for a bigger snake one day and get two 20 gallons. It would be about the same size as one 40 gallon.
If you don't have room or money, and don't care about space. Depending on the age of your ball pythons you can go out and get two appropriately sized tubs for them.
If they are hatchlings-yearlings a 15quart will probably work perfectly. If they are older, or too large, a 32quart could probably hold most adults except for larger females which might have to go to 41quarts.