Gun shop, gun shows, want ads.
Check the Beretta website.
50-1000 usd
Contact Beretta.
Contact Ruger Customer Service through their website.
There is no such thing as a "9mm Beretta" cartridge. Beretta firearms were manufactured in 9x19mm (also known as 9mm Parabellum or 9mm Luger), 9x17 (also known as the .380 ACP), and some models are made in 9x21 IMI for countries which prohibit civilians from owning firearms chambered in military calibres. The cartridge appropriate for your Beretta 9mm should be marked on the frame and slide.
9mm Parabellum
9mm Parabellum- often called 9mm Luger.
380 ACP or 9mm short or 9mm corto
Beretta made a LOT of different 9mm pistols. However, if you are asking about the M9 pistol used by the US Army, it is about 8.5 inches long.
First it is Beretta, second, it is a magazine, not a clip. There are several different 9mm models made by Beretta- it will use the magazine made for that model.
100-400 USD
100-450