Inspired by swissrifles.com
So the real ones cost $50 eh?
I can do better than that.
$2.39 1 & 1/4 inch inside diameter shaft locking collar with set screw from the hardware store
$0.25 hex head screw to fit threads on clamp
$0.00 ? hex head wrench from the pile floating around in the bottom of my tool box
Toss the set screw in the tool box to "replace" the wrench you took out. Dremel and file down the screw tip so that it will fit in the sight slot on the K31. Make sure it is round and true to center (as best you can). If you're fancy and sophisticated like me, dip the screw in cold blue to prevent rust on the bare metal left after grinding and filing.
Works like a charm!
If you build one and use it, you are required to say out loud "God bless MRW" every time you turn the wrench
or at least don't make fun of my wife's "fruity" Thanksgiving tablecloth