Start by removing the rubber seal at the top of the water bottle - it will no longer fit. The printed ring will insert into the groove it previously occupied. Print the ring, and clip it onto the bottle lid. Get an M3 bolt and insert it into hole. Then, get an M3 screw (I believe mine is 16mm) and thread it through to get it to grab the other side and cinch down the ring.
If it's slipping on the lid even after tightening, a small square of duct tape between the ring and the lid will be great at keeping it in one place.
Check out this and many other great prints…. at prusaprinters dot org! Sorry Linus - you've got plenty of opportunities for your own sponsor spots ;)
The author marked this model as their own original creation.