I know this doesn't have much to do with insulation, but I saw this a while ago and thought it'd make a nice pre-made underquilt, waiting for a stuffing.
http://www.ebay.co.uk/itm/British-A...Survival-Mattress-Personal-Gear-/271492332371
[no connection with the seller - just saw it and thought I have an idea...]
http://www.ebay.co.uk/itm/British-A...Survival-Mattress-Personal-Gear-/271492332371
[no connection with the seller - just saw it and thought I have an idea...]