Fridge vent covers. How do they stay on?

[acropolis22]

Winter covers for fridge vents came with the van. I assume they are the right ones. They seem to fit OK. But I think they need some sort of clips to keep them in place. What are these called and where can I source them? I'm sure someone knows. The blurry picture shows the spot that seems to need a clip of some sort.

 

[wiljoy]

There should be some turn knibs in the vacant holes. They keep the vent in place

 

[tonka]

You are missing the "turnbuckles".. can get them off eBay.

 

[acropolis22]

Have you seen the prices for a couple of tiny bits of plastic!!!!!!!
Managed to find some 3D printed ones for a slightly less eye watering price. Thanks to all.