In the FAQ there is a list of a couple of places. I was in a Cabela's once and found one that extends on both sides for about $9. It was made by Carlson, the company that makes choke tubes. I wanted another couple of them and I went to Carlson's website and couldn't find them. I also emailed Carlson's and didn't get a reply. I have bought Carlson choke tubes before. They have a rifled choke tube, I bought one for my factory fitted turkey barrel and it now shoots the BuckHammers very well. I have not checked the Cabela's online catalog yet. A hammer extension for the Ruger Blackhawk will also fit. I think Uncle Mike's has one listed.