Isaac,
That is a good answer. Infact better than most. If it is stainless, that can survive. I have seen some where the owner replaced those with an aluminum fitting that has a rubber gasket and they use the original self-tapping screw. This is a problem down the road because that self tapping screw corrodes and then will not come out of the aluminum. Boy, won't it NOT come out......
In the OE mushroom buttons, the screws were not exposed to the weather. That was good for the screws, but the buttons died of sun poising.
One of the small and little known features of the OE plastic buttons was that if you needed to get the latch out of the situation and the screws were uncooperative, a sharp chisel could cut the caps off of the buttons.
Don't even try to print the internal threads. Just make it a round (within the capability of 3D printing) that is about the tap drill for the screw.
Matt