Craig, I went to Ace to get 3/8" push caps while I was out running errands. They looked like the originals I have seen. Well, when I went to put them on, they were too small, more like 1/4". They must have been in the wrong bin at Ace. That was annoying.
So then... I went to a different Ace closer to home and that one did not have what I will call the original style. They had a thinner less substantial looking version which is what I bought and put on. I still like them more than plastic caps but I agree they may be a little small.
These smaller ones are shaped like a boaters hat and have just two small tabs that keep them clipped to the axle rather than a star sort of pattern I am used to on both the plastic caps as well as the original metal ones.
Sorry for the long reply....