Sure
Clay can be obtained all over the vast map in relatively every biome, in addition to the extensive and substantial bodies of water. The considerabley small amounts of complaints or the lack of dissatisfaction shown in there not being an abundant or adequate source of clay on the map validates my assurance that clay is effortless, or easy if you will, to obtain.
In addition, all forms of colored dyes can be obtained in numerous places, therefore I am lead to believe that dyes are as easily obtainable as clay and/or crafted.
In conclusion, I trust you understand why we have failed to add clay to the shops.