I think there are four options now for stringing if you don't do your own, and they are ranked below, from low- to high-confidence:
1. Multi-sport box store (examples would be Sports Authority and Dick's Sporting Goods).
2. Two-sport retail storefront (typically running and racquet sports).
3. Local tennis shop, in particular one associated with a solid tennis club.
4. Home or professional stringing service.
Then a separate matter is having/acquiring the ability to distinguish the service you need and providing the related input to the stringer. Of course you can learn as you go along too.