This is actually more of a remix of https://www.thingiverse.com/thing:3222693 - But I adapted it for the eye of agamotto. This AAA holder will allow you to just nicely squeeze two AAA batteries in the back. I used small copper wire to link one side of the positive and negative battery terminals together and then used stringed copper wire to tie it together and twist them on the other terminals.
Used a single 5mm white LED and green eye that I also made here: https://www.thingiverse.com/thing:3514964
Glued it to the back using 3dGloop. Drilled a hole in the center to fit the two positive and negative wires. Requires no resistor. Easy to install and take on the go.