I recently purchased some Fatshark Dominator HDO goggles to replace my Dominator HD2s and was looking for a lens protector but didn't find one that I liked. They are either the type that slide into the slots for diopter lenses or bulky ones that almost cover the entire goggle.
These are designed to be printed in TPU and lightly snap into place, you can watch the video to see how to install them. The little hook shaped pieces in the back for into the pill shaped holes to the side of either lens, not the slots for the diopter lenses.
There are 3 versions available. One with a tab to pull on to remove the protector, one without the tab and one with slots to put the protector on the goggle strap. With the strap version you can not feel the protector against your head.