Help to identify this craft item?

[SummaLuvin]

Can anyone identify what the item in the pictures is called? I want to buy more for an upcoming craft project but can't figure out what they are called to be able to find and buy them. They feel like a rigid plastic. Photo with my thumb for scale, approx 1.5cm wide and 0.5cm in height.

Google jewellery findings end cap or bell cap.

An extra large bead cap?

@ODFOx Thank you so much! I spent far too long trawling craft and haberdashery websites earlier.

@Knittedfairies amazing, thank you :)