No clue how this hasn't dropped in price yet, but I'll go ahead and state it outright. Demand for this has fallen and now people can easily buy this for a key. Also if you're wondering, I bought mine for a key.

1.35 keys is about 1 key + 2 ref btw.

Classifieds have plenty (almost 15 at time of suggestion) of 1-1.3 key sellers:

http://backpack.tf/classifieds/search/hard%20hat

Outpost sellers for 1.35 keys or less:

http://www.tf2outpost.com/trade/12612964 -1 key

http://www.tf2outpost.com/trade/12559474 -1 key

http://www.tf2outpost.com/trade/12590234 -1 key + 1.33

http://www.tf2outpost.com/trade/12654731 -1 key + 1 ref

http://www.tf2outpost.com/trade/12607352 -1 key + 1 ref

http://www.tf2outpost.com/trade/12609486 -1 key

http://www.tf2outpost.com/trade/12594237 -1 key + 2 ref

http://www.tf2outpost.com/trade/12578239 -1.2 keys

http://www.tf2outpost.com/trade/12641680 -1 key + 2 ref

http://www.tf2outpost.com/trade/12523475 -1 key + 1.66

http://www.tf2outpost.com/trade/12590234 -1 key + 1.33

http://www.tf2outpost.com/trade/12560541 -1 key + 1 ref

http://www.tf2outpost.com/trade/12643056 -1 key + 1 ref

http://www.tf2outpost.com/trade/12517277 -1 key + 2 ref

http://www.tf2outpost.com/trade/12632071 -1 key + 1.33

http://www.tf2outpost.com/trade/12557155 -1 key + 2 ref

http://www.tf2outpost.com/trade/12554307 -1.2 keys

http://www.tf2outpost.com/trade/12621890 -1 key + 1 ref

http://www.tf2outpost.com/trade/12655797 -1 key + 2 ref

http://www.tf2outpost.com/trade/12637692 -1 key + 0.66. Selling several.

UNSOLDS: Many other sellers are selling for 1.4-1.6 keys with little to no luck:

http://www.tf2outpost.com/trade/12657256 -1.6 keys

http://www.tf2outpost.com/trade/12522018 -8 ref (1.44 keys)

http://www.tf2outpost.com/trade/12613757 -1.6 keys

http://www.tf2outpost.com/trade/12163049 -1.6 keys

http://www.tf2outpost.com/trade/12573264 -1 key + 3 ref

http://www.tf2outpost.com/trade/12540789 -1 key + 3 ref

http://www.tf2outpost.com/trade/12433323 -1 key + 3 ref. 6 days old

http://www.tf2outpost.com/trade/12373207 -1 key + 3 ref

http://www.tf2outpost.com/trade/12361950 -1 key + 3 ref

http://www.tf2outpost.com/trade/11983035 -1.5 keys

http://www.tf2outpost.com/trade/12451158 -1.5 keys

Can provide more sellers if needed.