I may be able to help.
I attended a Johnny Stout Hammer-In late last year and we made mosaic pins. I can go back and look at my notes but I believe this is most of it.
#1 Design your pattern. Make sure that you develop an interior layout that will not be too loose and looks like you want. The ones we worked with were comprised of a 12 inch sleeve pin with various 12 inch smaller pins placed inside.
#2 Get a brake bleeder system from your local parts store. You are just going to need the vacuum pump part of it along with one of the transparent hoses that will fit over the end of the sleeve pin that is holding thi other pins that comprise your pattern.
#3 Mix some slow cure epoxy. Make sure its slow becuase you want to have time to add the colorant or pigment and get it fully mixed. Mix more that you will need. - It sucks when you dont have as much as you thought.
#4 Stick the bottom of the mosaic pin into the epoxy and use the brake bleeder to pull a vacuum and suck the epoxy up through the sleeve pins that is holding your smaller pins.
#5 When you see the epoxy come out at the top through the transparent tube, your mosaic pin should be full of epoxy.
#6 Pull the pin out of the epoxy and place a piece of tape across the bottom and then remove the tube from the top. Sit it upright to cure for 24 hours.
CAUTION - The reaction of the epoxy is exothermic and the pin will get HOT! Way hotter than most people realize. - I can tell you from experience.
I hope this helps. I have seen it work and the results were just as good as any of the pre-made ones. And way cheaper.
Lonestar JR