I originally purchased these tumbled tiles at The Home Depot. I have heard that some locations no longer carry them. I have also seen them at Lowe's and at this link on Amazon.com: Tumbled tiles by Oracle
For best results: use Stazon Ink for both Stamping and coloring to guarantee no fading, bleeding or running when wet. Other coloring methods may work but you should experiment prior to gift giving to make sure they don't run when wet.