I'd recommend getting a fan cooled 532nm or other wavelength laser. These usually run off 12 volts which you can supply using a battery pack. They can generally run as long as the battery hasn't discharged. I have several I got awhile ago on eBay.
What is the designs purpose? That may help us find something closer to what you're looking for.
Unless it's to keep Tom Cruise out of your vault, that mission would be impossible.