Where do you great sheath makers on here purchase you leather?
Leather Factory - Tandy's. I use 7-8 oz vegtan leather.
I can't speak for the "great sheath makers", but Tandy's seems to be really good for not so great sheath makers. The guys in my local shop are always very helpful when I show up with a question or problem.
I'm definitely not a "great sheath maker" but purchase veg tanned sides or shoulders from Tandy in varying weights from 4-9 oz thicknesses. I keep quite a bit on hand and select the weight according to knife size. Also purchase inlay material from them as well, such as stingray, ostrich leg skin, etc.
Wicket and Craig
http://www.wickett-craig.com/
Another vote for Wicket and Craig. I get their utility grade and it is better quality that Tandy sells.
Siegal(sp?) leather in North Carolina
Tandy is fine, and very affordable, they offer several grades. Best bet is to find a store and actually sort through the lot.
If you dont mind spending extra $$, another vote for Wickett & Craig.
I know Paul Long uses Wicket & Craig, I've never tryed it.
I just split my Saddle skirting leather for any sheaths. I use Herman Oak skirting and buy it by the roll.
Springfield Leather Company is a great place to deal with. They sell Herman Oak Leather by the square foot instead of making you buy a whole side like most place, and their customer service is awesome.
Thanks for your help, leather has been ordered!