Call Thompson Center. I had some questions about my sights since I wanted to go to a peep sight and they were very helpful. When I ordered parts I went directly to them via their website.
I love my Black Diamond XR in Stainless Steel. Mine has stayed in better shape than my buddies which was a blued barrel. It's not about care either because my buddy is very meticulous when cleaning his gun. Not sure what muzzy I would buy now. I spent a lot of time on this forum and others asking a lot of questions before I settled on the TCBDXR. Hope you find the part you need and at a great price.