G'day IinT, good project and one I'm soon to undertake as well. Instead of riveting the small-buckle strap on you can stitch it if you have an "eazi-stitch" or awl and needles.You can also stitch in a certain design or pattern if you like. This is probably more time consuming but I'd say it'd be stronger. That said, rivets are strong and will be more than adequate. Just a "look" option. Also you need to take it easy riveting leather as you can pinch it and cut right through if you go too hard with the hammering.
Cheap/burred buckle can be filed down if you need to.
Erin