Nissan Leaf's Aerodynamics require a floor of fiberglas below the motor/drivetrain.
I was replacing my brake fluid today and dropped the cap down beyond the point of no return. I wasn't going to take the whole bottom off the car just for a little plastic cap.
I couldn't find a cap that would fit so I measured it out. 34mm widest point, 28mm cylinder around the top. This is designed to screw onto the existing threads.
I found the part for $13 on Nissan's website, but hey, 3D printer.
Here's the source model for adjusting: https://www.tinkercad.com/things/7JAe1vDGpbW-brake-fluid-cap/edit
My first prototype (that seemed to work after re-shaping), had no grip so I added edges, as well as adjusting the measurements slightly.
It was brought to my attention that brake fluid is very sensitive to moisture. Having just 2-4% H2O moisture in fluid changes the freezing and boiling temperature of the fluid. See moisture related brake failures, I recommend spraying the underside of the cap with Flex Seal or another alternative that gives the cap a water tight seal when twisted tight. Anybody who has printed a cup should know prints can't hold out any kind of liquid.
Don't run this cap for more than a few days without some sort of seal. This would be a great temporary cap but shouldn't be trusted for long term use.
Takes about 30 minutes with 2 shells.