Whoever needs Granite ;-)
What's your business model? Can you sell on mass? If so, perhaps target large kitchen/ bathroom retailers- although I suspect they have already exclusive deals in place with other suppliers- I don't know that market, but Magnet, wren living, BandQ, howdens off the top of my head, smaller options would be local fitters/ kitchen suppliers and see if you can agree a supply deal for them?
Do you cut /supply to individual customer specifications? If so, you need a direct to consumer method, I've seen a number of websites for this, where I as a customer can put in specific measurements for my kitchen, get a price including a safety measure up by a specialist before they order and cut/ supply.
Just my thoughts, not conclusive, but 5 minutes worth of spare time for you!