its usually an attachment accessory, sometimes not part of being attached to the camera body...some is totally seperate, but connected through a cable.
Do note that GPS only work outdoors or last-known location, cause it connects via. satellite in the skies...need to be unobstructed.
quite a few models, depends on what brand/system, you may want to talk to Cathay photo, John 3:16, etc. bigger professional stores...but dun ask Courts or those wannabe small stores, they will only smoke you.