Ken,
If you don't have any, Look thru thrift shops for leather items you can buy cheap to practice on.
A fellow member just told me, he'd bought a 2nd-3rd (?) hand leather sofa cheap that supplied plenty of Cow skin.
Been told furniture, upholstery stores sometimes have sample books with discontinued lines you can buy.
I'm not sure what size the rivets are, but do know you can buy them cheap to practice with from these guys:
Solid Rivet Installation Tools | Semi-Tubular Rivet Tools | Jay-Cee Sales & Rivet, Inc.

PS: Seen the Bhama boys ?