Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:1816753.

This is my take on a concealed toilet seat fixing, made due to the original falling apart before it was properly fitted.

I hope others may find it useful.

The bolt is a 5mm and the nut size is 8mm across, it should be a easy press fit.

I recommend that the parts be printed in this orientation with 100% infill as very little cleanup is needed.