Track may have a parts set. A lot of their parts sets are incomplete and have been for years. I used 13/16" barrel for a build. At the time I like the idea of lighter. Now I would use a heavier, more authentic barrel. Also a bolster in a 45 cal 13/16" barrel may be a bit sketchy.
Be aware that the butplate is not usable with a modern shooting stance. You may have to modify it.