29mm Blanking Plug for Plastic Shelving Racking Unit

I was putting up some 4 tier plastic garden shelves and I've noticed that I have 2 blanking plugs on top missing. It looks weird and water will also get inside. I couldn't find even similar model anywhere so I've decided to create my own. Original plug is on left (second photo) and mine have exactly same dimensions (right). I've printed 4 to have them matching and they fit perfectly well and you can still remove them with a push. Last photo shows how whole 4 tier racking looks like.