As far as I know, there are two licensed sets of FFVII pins plus a number of unlicensed ones.

There are 6 Official Final Fantasy VII Pins. The set was released by Bandai in 1997, and the pins could only be acquired from the Gashapon toy dispensers for a limited time. The pins came in a capsule with a paper insert. The 6 different pins are Chocobo (A), Chocobo (B), Cloud, Aerith, Barret and Red XIII. The Chocobo (A) is said to be slightly rarer than the other pins of this set.

The other licensed pin set consists of 3 different pins. They could be purchased for a limited time in Japan in 1997.

There are also a lot of unlicensed FFVII related buttons and unlicensed FFVII pins featuring Cloud and Sephiroth.