Bazemk1979 had an IC up for a GB to do marble wrist rests. Not sure where it's gone but I know it's still active.
I'm waiting on my friend that we are working together to hook me up with his cousin that has counter top business. But job has been keeping us busy and I never got introduced to his cousin. Once when I meet him, I will tell him I need lots of scraps, buy them for cheapo and start making some granite wrist rest in different sizes. I can cut them,round and polish the edges my self. Most likely wont be anything GB related but I would like to keep the prices lowish, depending on size of the wrist rest somewhere around 30-45 USD.
BTW OP that's onyx marble, its not bad wont break easy, but you dropped it once there is a high chance that it will either chipout or break. Onyx is famous by its colors and its light colored texture, but its soft stone that's why its easy to be cut.
Here is a pic from a huge backsplash I did 4 years a go, everything was glued with 100% silicone on the panels, I had to be careful how I figure out the layout on ut because behind the panels there was LED's installed and in case an LED died they should be able to remove that panel and replace it LOL. Was real tricky job, but anything is doable. Oh yeas and that's Onyx btw.