This is a short article on chamber sleeving by Diggory Hadoke. I considered it on a 10, but ended up selling the gun instead.

https://www.vintageguns.co.uk/articles/chamber-sleeving/

Briley can do the work although I am sure there are people who are more specialized.

https://www.brileygunsmithing.com/c-879-full-list-of-shotgun-gunsmithing-pricing.aspx