I've notice that the Hydro5 razor blade case has been lacking the cover lately. (And I'm sure that anyone that uses this brand of razor blades have notice as well). So, with the one I still have, I made this. 

print settings: because of the wall thickness, you don't need to worry about infill. But layer height I recommend 0.07mm. 

This was done on my Prusa mini with a 0.4mm nozzle.