There are a few rebuilders in the US, Soundsmith, VAS, Joseph, needlestein from ak where he was always advertising his service without being a vendor so he got punted but set up shop on ebay and Andy.
https://www.sound-smith.com/services/cartridge-rebuilding-retipping
https://vasnyinc.com/repair-service/
https://www.ebay.com/usr/cartridge_retipping-5?_trksid=p2047675.l2559
http://www.phonocartridgeretipping.com/
Soundsmith will be costly, take a bit of time but may be the best. VAS is very good. (both from reading what folks have received after sending in a cartridge for repair.). Don't know Joseph's work. Andy is on the left coast.
Then there is the UK (Expert Stylus) and Aus (Chris, cafe latte on ak) that have folks that do this work, too.
I need to get about 10 cartridges looked at and 1 needs a suspension rebuild, one needs a cantilever so I have been collecting this info in my mind, now I know where to look to find the list when I finally decide to do something. VAS may have first shot, you can sent in cartridges for a viewing for short money, something I could do if I had a stylus microscope. But the last one that floated through the bay for cheap was bought before I read my alert about it.
Seems most are using built stylus assemblies, cantilevers with nails attached. Differences are what the material of the cantilever is and the shape of the diamond.