I had so much fun making game grippers ~10years ago. I'd be open to making some for the pro1. One problem is I live in the USA and this seems to be primarily an EU phone. I'd probably need to track down my old EU partner or even better if fxtec would distribute them.
I tried connecting with those guys on LinkedIn about the pro1 but no reply.
For a little history, the game gripper came before we had decent Bluetooth game pads. Once they stopped making high end phones with slide out keyboards the game gripper stopped selling and I went back to work.