Need Hardware Assistance

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I have never in my life assembled a snap, or popped a rivet. I'm assembling my holster, which is made of two layers of 8/9 oz. leather. Then I'll have a belt loop that buttons to the holster. I'm trying to mimic this holster from Brigade. The piece of leather that folds around on the top/slide side of the gun is simple, aside from determining what size shaft is required (which I don't know how to figure). The butt/grip side of the holster is a snap, plus a rivet or screw of some sort to attach the leather piece to the backside of the holster.

Can someone please help me determine what items I need to order to assemble this bloody thing? I don't know the terminology for the components, and how to determine sizes, so I don't really know what to order...