Hmm. well you've got a couple of options.

1) buy an expensive board that can be easily configured with extra stepper drivers like the duet3d - at the end of the day the printer was free, so all you'd have invested would be the cost of the board - and even a pricey board = a cheap printer.

2) look for a cheap second hand model of the same printer that has problems with ANYTHING except the board. That way you not only get the board but a whole bunch of spare parts as well :-)

3) what cliff said :-)