Rusty Sherrick makes one similar to that (and he is an old timer that was around back then).
DeSantis makes some, but he was not in business at the time the movie was made.
There is a "Miami Vice" holster that holds the weapons upside down (more or less), but has place for a spare clip on the other side. I don't recall seeing one set up for revolvers.
Pachino carried a model 36 revolver as I recall and a Beretta 9mm (service size). You don't say which weapon you are referring to.