I highly, highly doubt that anyone will ever be in the same situation I was in and have access to a 3D printer, but if you are here's a part for you.

The button assembly for my toilet broke. The previous owners of the house had bought another assembly, but it was too small to use with the retaining nut that came with the toilet, and the button was too small for the hole in the lid.

So, I modeled the broken assembly and then created inner threads to insert the new assembly. It uses the same finish ring as the original with the new one sitting on top of it.

I'll also upload the Fusion360 file so you can tweak it to make it your own.