This needs a drop.

Classified ads at the time of posting:

http://backpack.tf/classifieds?item=Warmth+Preserver&quality=11&tradable=1&craftable=1

3*1.47 keys (1 has Assists)

Unsold at 1 key and 10 refined (~1.5 keys):

http://www.tf2outpost.com/trade/26258719 (~1 week)

Unsolds at 1 key and 9 refined (~1.5 keys):

http://www.tf2outpost.com/trade/26361929 (~1 day, young)

http://www.tf2outpost.com/trade/26293545 (Has Assists, ~1 week)

Seller at 1 key and 6.33 refined (~1.3 keys):

http://www.tf2outpost.com/trade/26349496 (Has Voices From Below, ~2 days old)

This is all I could find on Outpost that are valid at the time of posting this suggestion.