Making your own stamps is not difficult if you start with the right materials! I find that stainless steel Hex headed bolts with a shaft diameter of 1/4 to 5/16 inch, thread free shaft for 4 inches will be ideal. The hex head is adequate in size for most of the stamps you will need. The head can be shaped roughly to size by a grinder or belt grinder. Needle files and checkering (parallel line) files are used to finalize the shape prior to buffing. Rusty stamps will not be a problem and if struck with mauls, mallets, or striking sticks, will outlast the user.
I have made 95% of my stamps over the years. During this time I realized that most of my carving and stamping of leather was done with less than 20 stamps. It is not how many stamps you have that makes you a craftsman, it is how you use the stamps you have.
Although many stamps are simple to make, stamps such as good basket weave and other complex types are best purchased from the professionals. As is usual in such instances, you get what you pay for!! ---Sandy Morrissey---