I've had my eye on buying a wine fridge for a while, for just this purpose. I've tried the ice chest routine, but the temps kept fluctuating too much. If you have a wine fridge, try 60 - 65 degrees, and see how they do. They won't survive for weeks or anything, but they'll definitely slow down for a few days. Just have good chow and a warm place for them to recover from the big chill.
The big caterpillars can go into a regular fridge at 40 degrees for a few days, then out for a while. This actually worked for me. I put them through a few cycles, but then I forgot about the poor things and left them in. Ewww. Talk about scary stuff in the fridge - mummified blue worms... :shock: