Have you tried your local gun shops? Gunbroker.com or gunsamerica.com auctionarms are online options, but you will need to have a permit to buy and a local FFL dealer to handle the exchange. The usual charge is around $25 to transfer. Expect to pay shipping on top of price paid.
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.
Contact Beretta.
9mm Parabellum
9mm Parabellum- often called 9mm Luger.
Check the Beretta website.
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
Look on the frame
9mm beretta
@ 7 H and 7 L