There are many repair stations in the USA that can reweb seatbelts for USA registered aircraft.
Tag worn off? That's a purely argumentative question. Millions of parts have the identification painted over, worn off, damaged, faded, destroyed etc. It was airworthy when installed, its still airworthy if:
- Not a life limited part, which requires positive identification and tracking, or can be tracked back to the last maintenance release with times & cycles recorded and total accumulated times & cycles can be summed.
- No Airworthiness Directive requiring similar as above.
- Still operating and functioning properly.
This reply answered the OP question. If the belts are still considered airworthy, he can carry on. Bell206 elaborated on it. Lack of a tag does not render them unairworthy. If that were the case, every plane would sit!
Maybe they are 6 months old and the tag got ripped off yet are virtually new. Maybe they are 6 years old and in tatters. Hard to say over the internet.