I am looking for companies that develop or supply mouthwash
formulations, preferably a company located in the U.S.

I previously worked on this question without success.  The customer is
seeking information regarding companies with the capability to develop
a custom mouthwash formulation for him, not companies that merely
manufacture store brand/private label mouthwash or will bottle a
custom formulation to his specifications.  The mouthwash formulation
development capability is critical.

Good luck.

Wonko