There's a ton of single action 357MAG revolvers out there with 7 1/2" or longer barrels, from a bunch of different makers if you consider used as well as new -and quite a few double action models with longer barrels as well that can be found new or used.
I've had quite few 357MAG revolvers over the years, including several SA's and 2 or 3 DA's with 7 1/2" to 10 1/2" barrels. But since you made no mention of your intended use.....