This is basically a goggle holder for an airsoft helmet
i did it for my FMA goggle with a band of 35mm
I simply passed the elastic band in the piece that I printed and sewed it with the sewing machine. On one of the two sides, I also added a loop to adjust the length to center the glasses.
If you do not have anything to sew you can try with rivels.
If you prefer you can also put this piece on the top rail of the helmet
If you have any question just ask ;)