They are a regular production item, although produced in far fewer numbers than other Glock models. A few police forces have purchased them, but I'm not aware of any military that has adopted them except in limited numbers for special roles (Portugal bought quite a few, but for what purpose I don't know).
Those in the US have come from the IRS, DEA, and EPA purchases, as well as a few major police departments (LA and NYC).
Why would the EPA need guns??