GTS sun visor end caps

I just noticed one of the clear plastic end caps on my roller shade sun visor is missing. I was thinking about replacing it with a clear vinyl screw-thread protector of the right diameter but I can't find one anywhere. Any bright ideas for a solution that looks more or less correct?

 

I have the suction cups, what I’m looking fo are the clear end pieces that slide over the rod at one end of the roller blind. It looks like a small enough screw thread protector would work, but I haven’t been able to find them in clear.

 

They aren’t, although maybe I could cut the flange down to fit. I suspect 8mm is too wide though.

 

That looks exactly right. I wonder what a “headband end” is though - half the battle with these sorts of treasure hunts is finding the right search terms.