Have you a non slip paint that can be applied on to external quarry tiles
It depends how porous the quarry tiles are, some acccept a coating and some don’t so unfortunately no straight answer to that.
You would need to do a test area first but the product that may work is Coo-Var Anti-Slip Acrylic Floor Paint.
Primer: Thinned down first coat of Coo-Var Acrylic Floor Paint.