This is the aero version of the standard 1515 (for 8020 aluminum extrusion) rail button using the NACA0020 airfoil.

There are four versions you can download:
1) #8-32 machine screw
2) #10-32 machine screw
3) Rounded
4) Unrounded

The hole for the flat-headed screw has a counter-sink in it.

https://www.thingiverse.com/thing:4600247