The slider will work fine without the rear (or front depending on your point of view) bakelite piece, Doc. What happens (I think) is the slot in the bakelite wears a bit over the years allowing the knob rod to slide a bit further in when the lights are turned off. Then when the switch starts being harder to pull out and push back in (lack of lubrication, age, wear, whatever) somebody pushes the switch in a little too hard and pow...out goes the end of the bakelite slider piece. The tip end of the rod is sharp and there's only a few thousands of clearance when the switch is new. At the point the bakelite pieces get knocked off, the switch is on borrowed time because no longer can it slide all the way in and the switch can not be predictably turned off until that is fixed. But if you notice on the first switch I repaired, the end of the slider was gone, and that one is working fine. In fact, I'm using it in my truck. A 3-D printer would be neat, but that's way down on my list.
