Here are different designs of shelves pins. The diameter of the pins are 6mm and should fit all standard shelves pin holes.
I myself don't like plastic shelf pins and prefer to use metal ones, but these can be useful anyway. I would print it at 100% infill for strength.
This object was made in Tinkercad. Edit it online
https://www.tinkercad.com/things/fUVnr5pTtjL
fUVnr5pTtjL.stl | 188.5KB | |
I_shelf_pin.stl | 11.4KB | |
L_shelf_pin.stl | 6.6KB | |
O_shelf_pin.stl | 51.4KB | |
P_shelf_pin.stl | 34.4KB | |
V_shelf_pin.stl | 124.3KB |