I want to adhere stones/crystal to belt buckle bases.?

I am wanting to create my own belt buckles using blank bases (silver tone). I found those online but need to figure out how to adhere the stones to the base. They need to be really permanent as I may sell them.
Thanks!

Devcon 5 minute or 2 ton epoxy works great and dries clear i use them on my knife handles, comes in two bottles and you mix it together

Crystal Silver Tone
Crystal Silver Tone
Crystal Silver Tone