There are a few ways to make your own selling pins. You can either use a commercial pin maker, make them yourself using a die cutter and metal stamping kit, or use a laser cutter or CNC router. If you want to use a commercial pin maker, there are a few different ones on the market. They all work in basically the same way - you create a design in software, send it to the machine, and it prints it out onto metal sheets which are then cut into pins. The downside to this is that it can be quite expensive - the machines start at around $2000 and go up from there.