Duncan suggests Swaygo bags. They're not cheap, but they seal like a drybag and are extremely durable - in fact they're intended to be dragged through the cave like a tacklesack. We've been using them in China for a few years now, and transport them inside tacklesacks; so far they have never let us down. The largest size (called 'sink' for some reason) is just right for 24v Bosch drills. I reckon that CUCC's Makitas should fit in the medium size ('pit').