Ha ha! Yes, those bulbs have a spec for voltage. Rewire the string as "series-parallel" with enough lamps in each series string to work properly on 12 volts. It will result in wiring changes that might be more trouble than it's worth.
They draw so little power though, I think an under $20 inverter would power them just fine like Wayne suggested. Even WalMart has ones in the $20 range.