No such list exists for the most part.
I have seen magazine articles in the past that listed what guns State police agencies used, but nothing else.
Considering that there are many thousands of local police departments, college police, sheriff departments, State police, State investigative agencies, and Federal law enforcement, coming up with a list would be almost impossible.
Another factor is time frame. In the past most law enforcement use the same guns for many years.
These days they seem to change pretty often.
So, how big the data base would be depends on how far back you want to go.
If you go only by today, you can rule out revolvers, and just list any 9mm, .40, or .45 automatic pistol made in America or in Europe by a major gun company.
That means Glock, S&W, Ruger, Colt, H&K, Sig Sauer, etc.
There are...or at least...were some agencies that had an approved list of handguns for officers who chose to provide their own rather than carry the issued sidearm. Some agencies have also required the officer to provide his own but specified what make and model it had to be.