This is a gas mask adapter - https://www.draegershop.co.uk/draegeruk/en/GBP/Products/Respiratory-Protection/Respiratory-Masks/Full-Face-Masks/Plug-in-filter-adapter-P-RA/p/6736770 .
Printed and tested. Everything fits right, just like the original from the link above.

Note: Not tested in high temperatures, when firefighting.