Tandy leather factory. You can also make collars with nylon webbing, they will make it longer and the webbing is cheaper than leather. I make collars if you want some good Ideas, check out my website
www.rollingthunderec.com. If you take the link to my facebook page you can see a instructional video I made. I designed one that will stop a .22lr at point blank range. I have never had my collars cut through