I didn't like the flat version that others have made as it pokes/irritates my skin when I look up (not much hair!). I've printed these in both PLA and PETG and both work fine. I have two versions, V1 is more basic and prints slightly easier/faster, but is a little more rough to handle. V2 isn't as harsh to use and doesn't add much more time to the print, and has a little less material used.
I've been printing these at 100% infill as it doesn't make much difference vs 0% in time or material. PETG is a little more flexible and conforms to your head a little easier.
Printed at 0.3mm/draft layer height, less than 30mins each.