I have been braiding whips since 1978, apprenticed with David Morgan for 9 years. I am buying my leather from Hardtke Leather and I just bought 20 hides from them 2 weeks ago. The quality was very good, and I got them in a week. For whipmaking I buy a certain tannage of kangaroo leather, drum stuffed, ask Peter Hardtke which is best for your work Their web page is www.hardtkeleather.com. Packer Leather is considered the best tanner of kangaroo hides in the world! I worked with Peter Hardtke one of the owners, email is : firstname.lastname@example.org. Good luck with your knee replacement!! I have a few hips and an ankle replacement myself.