https://github.com/pieeg-club/ironbci_3D_EEG_Printable_Headset
I believe the headset is ready, but some work is needed to start, cables, connect the electrodes, and attach the battery from your side. Looks like better to use a 200 mA battery

Dry Electrodes – no gel needed (As an example, I used this one - link
You can adjust the strength of the connection between the electrodes and the skin through the straps.

Watch the full tutorial video here:
https://youtu.be/x07X1MO13d0

Assembling
For final assembly, you'll need bolts, washers, and nuts. Also, a belt. Details on what you need and the dimensions are in the video (above) or in the folder with the presentation.

Material for 3D printer
TPU or PLA So Flexible is good. But take into mind that during printing

Final
I'm sure the flexible material is very good, but you see, you need to provide support during printing, which is difficult.
A rigid material is more difficult to adjust so the electrodes touch the skin.