Yes, check out your local garden center.
Alternatively you can use Miliput. Just make some thin sheets and use pincers to break them into pieces once the putty is cured.
if you flatten and roll fimo then fold it over and do the same again and again (like making puff pastry) when cured it cracks to give realistic slate..
depending where you are it\'s surprisingly easy to find ..soe area just don\'t get slate geographical reasons..
Most garden centres will let you take a sample handful to \"check the colour against your boundary wall\" a slack handfull can last a long time with minis..