I have been rehairing bows for 29 years. I purchased my bow hair from
Michael T Sowden in the UK, until I heard where he buys his hair from
(a man in the US who buys from a Chinese man in Qingdao, China). I
switched to TwoTree International in 2005, because they buy their hair
directly from the slaughterhouse. They also buy hair from living
horses. They go to the dressing facilities every year and purchase
new tails at the auction. Pretty cool!
Here for more info about TwoTree: http://twotreellc.ning.com
Here to buy the hair: http://bowhair.net
More about the owners here: http://luthiersupply.net