First, I would make a 1:1 scale copy of the lock from Tracks catalog. Cut out the picture and see if it fits on your rifle's mortice and place the pan and sear bar correctly. That being figured you could remove the drum. The pictures I see on line show flats on the drum to fit a wrench. You could use strips of pop can metal to protect the finish under the wrench. Use a large adjustable wrench with good condition jaws.
Finding a liner may be easy, or you may have to make it. It you are lucky the manufacturer makes one already that will drop in. Otherwise make on on a lathe. You could possibly get lucky and make one from an allen head grub screw depending on how the liner/drum hole was made
