edit: also have a look at the remix of edabu1ibir58 at thingiverse for better printability:
https://www.thingiverse.com/thing:5416120
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I "wear" my safety glasses all the time on my helmet (Dräger HPS 4300 / THW / Technisches Hilfswerk). Unfortunatly they always tend to slide over the helmet on the left side and get loose. There is a mount on the back to hold the head band and on the right side I put it under the flashlight mount. To also secure it on the left side I designed this little holder.
The holder consists of two parts. The main component which is put on the left helmet visor mount. The second part is the pin to fix the main part on the mount of the helmet. This pin can be pulled out easily to demount the safety glass holder.
Please keep in mind that this thing is no offical part and is not approved!
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My original design on Thingiverse:
The author marked this model as their own original creation.