It depends on the failure mode of the cap. If it has blown its dielectric, then chilling it may cause the plates to separate enough to boost the capacitance, but it is more likely to just be a waste of time.

Aside from that, you could strap on other capacitors as long as their voltage is the right value. A daisy chain of 50mf capacitors to shore up the blown capacitance might buy you a day or so of usage.

Best bet, if you have an old broken microwave nearby, would be to pull the cap from it and wire it in.