I used an offcut of trace heating cable years ago when my lathe was in an uninsulated shed: feed it inside/around the machine and it delivers gentle heat... e.g.

trace heating cable | eBay

... but TBH the only real solution is to insulate the heck out of the building rather than mess around with half measures on the tools themselves. Makes for a much more pleasant working environment too, and insulation also doubles as sound insulation so the neighbours won't complain.