I use a cheap (35 quid) wet-and-dry from Wickes. That's had 5 years of abuse sucking wood dust to lumps of plaster and just keeps going. Even the cheap plastic nozzle is great for sucking from around the cutter as nothing gets damaged. Cheap enough to be throwaway if it breaks. And lots of suck - probably beats a 12V device. Given that you are going to be near a mains supply anyway, and you are going to be clearing a lot of dust, a cheap mains vacuum is probably the way to go.