What you want are the 12 function keys on the left as these keyboards have. Then you can control movement with your right hand while using your left hand for spells / prayers.
Besides cost and availability, the main problem with the Avant Stellar is the placement of the vertical bar and backslash key. That's not a problem playing Angband, but that's a commonly used key in C*, UNIX, TeX, and DOS. It took me a while to become accustomed to the key being there.
The Gateway Anykey has my favorite keyboard layout, but it is lacking in tactile feel. I've never really enjoyed typing on it ... (My Anykey is version 5. Other versions may have better feel.)
I am currently using an original Matias TactilePro. I was using a wireless Logitech which had "a lot more keys", but this discussion about mechanically switched keyboards has reminded me that I can type much faster with my Matias. I would suggest checking out
Matias Keyboards if you are looking for a "good" keyboard in general. There's a lot of interesting products for sale for keyboard enthusiasts (but nothing with 12 function keys on the left).