I was at Brothers Machinery Exchange (North Andover, MA) today, and they have a Burke/Powermatic Millrite MVN (which looks like a slightly scaled down version of the MVI that I have). I had always wondered what the original knee gib locking screws looked like, as my MVI didn't have them and so I improvised using Holochrome 3/8-16 hex socket cap screws and hex wrenches. This works, but the hex wrenches fall out from time to time.
The MVI still had the original gib locking screws, so I took one out and looked it over. Very simple. They were machined from a bit of 5/8" square steel (1018?) bar machined to have a 3/8-16 threaded shaft ending with a full dog point. The dog point part is about 3/8" long, with a dished tip (so the brass ball will center properly).
The 5/8" square is the same as in used on the drawbar and on the knee Z-axis (up and down) crank, so one can use the one crank handle to perform all these functions.