E Class Brake Part Query

[Unininaninimity]

What do you call this part and is it easy to get hold of (see picture)?

The picture shows the one on the rear brake, but I need a replacement for the offside on the front brake.

The part on my car has lost its springiness, so it doesn't do what it is supposed to do. As a result, the front pad rattles on rumbling roads.

I took the car to my mechanic, but maybe he was busy and didn't have time to understand what I was asking, so failed to find anything wrong. After a very long hiatus to my erstwhile hobby as an amateur mechanic, it seems that I'm back in the saddle for this one.

Can anyone help?

 

[Uncle Benz]

I describe it as the “caliper outer tension spring” and the parts guy usually gets it right away.

 

[Unininaninimity]

Thanks for your advice, fella, much appreciated. I'll let you know how I get on.