I created a 3" diameter tool box to fit in the saddle spring.
When I build one of these, I start to realize the cost quoted for these. It takes a lot of time!
Simple materials (leather, thread, rivets, and a buckle), some tools, and time.
Next up is trimming loose threads and dyeing it black or brown.
A big thing to remember if you start one is the proper sequence of assembly. Need to rivet some parts together before you sew.up the box. Also, plan the sewing sequence so you don't block out an area to sew.