Manners thumb screw?

You should be able to take the stock screw to a Fastenal or a similar place and they can tell you the thread pitch. They may have the knob you are looking for there or you can search online once you know what thread is. I use a lot of Kydex cheekpieces and they come with a large knob. I replace them with a low profile knurled knob for some camera set up off of Amazon for a few bucks. Often if you are to purchase those types of knobs from Grainger, MSC or Fastenal they want to sell you a bag of 20 or something. Gets expensive if you only need 2.
 
I've been looking for one of these as well, like you dodge, I can't remember what company it was that produced these haha. If I get a chance soon, I'll run to fastenal and see what I can come up with. I may just call KMW and see if they have a recommendation or can give me the thread pitch of their loggerhead hardware.