The only one currently for sale is http://www.tf2outpost.com/trade/6801182 . It has a B/O of 1 Earbuds and a C/O of 20 dollars (~18 keys, though it depends on how much you consider the dollars-keys rate is). It was bought from a scammer who never listed it up on the Outpost.

The only other one of these I was able to track is owned by this guy http://www.tf2outpost.com/trade/5780784 . He seems to be a G. Fetti collector, and claims he overpaid for his. It's currently out of the market. Its history can be tracked here http://www.tf2outpost.com/trade/5345525 (the offers were hidden, so I can't be sure what was the trade). We can go deeper though and find this http://www.tf2outpost.com/trade/5287789 (traded for a Peace Bonnet (currently at the same range I'm suggesting now) and further down, this http://www.tf2outpost.com/trade/5159248 (asked for an Earbuds/28 keys).