You could try your local dollar store, or look at stone/travertine tile at your home improvement store (which would require cutting them to be round).
You could always make them yourself with quick set mortar or countertop concrete mix: https://youtu.be/Wyqagd53-ds Is there a ceramics shop in your area? Maybe they could make some for you too.
Other than that, more expensive routes would be to have some custom made by a company like Thirsty Stone Coasters, or use the sublimation ones with the DTG non-porous pretreatment if they are smooth coated.
You could always make them yourself with quick set mortar or countertop concrete mix: https://youtu.be/Wyqagd53-ds Is there a ceramics shop in your area? Maybe they could make some for you too.
Other than that, more expensive routes would be to have some custom made by a company like Thirsty Stone Coasters, or use the sublimation ones with the DTG non-porous pretreatment if they are smooth coated.
