Custom orders for gemstone cylinders for cufflink set

[NiceSmile]

Who do PS'ers recommend that I contact to find out about custom replacement colored gem cylinders for this interchangeable cufflink set I have?

Thank you

 

[chrono]

What type of stone is it?

 

[NiceSmile]

What type of stone is it?

looking for any type of stones. this is onyx here...