No, not a new hobbit from a Peter Jackson movie! I was looking at some ACW terrain on BT Sherman's 10mm blog - Very impressive and quite accurate. He uses blankets for an underlay, but given 10mm figures are not heavy, I should be able to get a good effect using upholstery foam. At 1/2" thick and 25.5" wide, it is a few cents under $9 a foot from a store within a 20 minute drive. I will have to get a couple of yards to experiment with - 4 yards will cover my table once. I hope it will prove adequately shape-able.
The trick is finding exactly the right fabric to go over it. While I would be surprised if it will all fit into a normal backpack, I should be able to assemble something that can be carried easily on transit.