What's the bracket used to fix a kitchen faucet called?

Question

I've got a broken kitchen tap/faucet, and it's because there is a plastic bracket that fits under the sink that has broken.

I need to know the name of it because I can't search for a replacement without knowing the correct search term!

It's got a 30MM hole in it and is otherwise triangular; it fits here (excuse the ascii art!)

   //==\\
   ||
   ||
   ||
  +||+      <-- faucet
----------  <-- sink level
  ||||      <-- plastic bracket goes here
  ----      <-- metal plate

This is the rough shape;

  <-------------------->
    \       ___       /
      \    /   \    /
        \  \___/  /
          \     /
            \_/

Answer 1

This is from an automotive store but it's the same thing: retaining washer.

(source)

Answer 2

if you cant find it, just find your local maker club and someone there can 3d print or machine it up for you.