I don't see a way to do that. You would have to have a device that is actually different like a
Razer Tartarus. In contrast this
Redragon K585 DITI, probably won't work because the Q key will be the same on the Keyboard and the One Handed Gaming Keyboard. Both Q keys will send the same signal through USB to the PC to tell it you pressed Q.
Not that the Razer is your only option. You will have to do the research yourself. I'm just reiterating what Baertram is saying such that you can't have a Keyboard with the same keys. The Razer has keys but it's more or less a joystick with 19 buttons. You could use the 19 buttons for keybinds. I could not play that way because like most people I use a Mouse and Keyboard. So I'm not saying that is a viable option because you don't have three hands.
Simply put your additional device has to have unique keys that are different from the Keyboard so that the game can see it is a completely different device.
DIY suggestion
Warning: Spoiler
Another thing to look into is making your own device although I have not had the patience to do so. The inspiration came from me looking at a Logitech G Adaptive Gaming Kit for use for my feet when I play Elite Dangerous. So you can make your own if you can read a lot and are willing to go through a lot of trial and error. Most videos use a Joystick and solder wires to the buttons on the Joystick. I have also seen an
Arduino used to make a Joystick so you could maybe build a button panel from that also but I think it does require some programming as well.