If you're not going to do a lot of the work yourself and need to have it done, check with one of our sponsors, MGM Barrels. They might be able to make the barrel you want, as well as install it.
Failing that I would see if any of our other sponsors can produce the barrel and services you may need and if there is no connection there then I would go to the Montana Rifleman which I know rebarrels lever actions. HTH. Mikey.