We do have suppliers of non/anti-slip phone mats. The rates posted on their site are usually on retail (ranging from $.45 - $5) so you may have to contact them directly for a wholesale price.
I have compiled a list for you of some of our top suppliers of this product.Link hidden: Login to viewLink hidden: Login to viewLink hidden: Login to viewLink hidden: Login to view
Just a tip: When you contact these companies, the best way to lower the price even further is by purchasing in bulk. Their prices are already very low, but if you buy 20+ units you should be able to negotiate the price even lower.
Please let me know if there is anything else I can help you with.