Well I said that I'd attempt to contribute some -

I like most have encountered this same problem, both the sagging fabric or the damage that some pins do; on the back of quite a few objects (I'll photograph some and post), I have secured (with epoxy), rare earth magnets found in old hard drives. On the back side of the apron, I hold a small steel washer or a second magnet and then of course the "pin" with a magnet secured to its back, on the front of the apron.

I suppose a single magnet of this sort on the back of the apron would suffice and allow you to just epoxy a small steel washer to the new pin, however, the two magnets together make it almost impossible to lose the pin.