Colubrids don't incubate their eggs, so the need for a fairly constant temperature is not as critical. The biggest danger they face is dehydration. The female will lay the eggs in the most hospitable environment, with appropriate humidity, and this sort of place is rarely available in an enclosure.
Without wanting to be negative - if you were attempting to breed them this year, why did you not have the equipment in place, ready for the event, even if it was unexpected... that's not advice that applies only to tree snakes - it applies to all species.
having said that, I've been caught out a couple of times, but atemporary incubator is easy to make with a foam esky, a heat cord (15 watts is usually plenty - don't go for anything higher) and a good thermostat.
Congrats anyway - and good luck with the eggs...
Jamie.