Grip tape. From my experience, the Hogue grip isn't going to help too much with the sweat aspect. It's also going to make the grip bulkier, which isn't something you're asking for.
Try and pick up some 3M from Lowes or Home Depot. That's what I use on my P2000, works fine, easy to find and cheap. I use it specifically for the whole sweaty aspect, but I only keep it on my right hand side. I didn't find it to help any with my support hand.