My favorite is Native Earth. http://www.nativearth.net/index.html
I've had my two button boots for 10 years, and this season I broke a button. I took the boots back to see if I could purchase a replacement button. The lovely young lady who assisted me went the extra mile in searching through their stock to find a matching button, then sewed it on for me. When I asked how much I owed, she replied, "Nothing." When I tipped her $10.00, she tried to tell me that it was too much. I reminded her that it was only a dollar a year for maintenance, and that seemed very reasonable to me.
Needless to say, I am pleased with both the product and the service.
*No monetary interest, no referral fees, no kickbacks. Just a satisfied customer.