Macbook white thingy below keyboard button is broken

I've got an early 2009 macbook pro, and I accidentally broke the white plastic mechanism underneath the S button. They are labeled 130 and 140 in the picture.

Does anyone have a clue what the white things under the key are named and where I can buy a cheap replacement?

They are sometimes called scissor clips. I have bought them from thebookyard.com, which is a Mac parts seller based in the UK. Apple is known to replace them for free as a walk up service at the Genius Bar and you of course can order official repair parts from a variety of sources.

Be aware that different keys on the same keyboard can have minute differences in the layout and size of these supporting clips even when the key cap size is identical.

Alright, it turned out that I'm looking for a so called B-Clip

The number of this piece is 221159039672 If you type in this number on eBay, you'll find the right white clip.

The other number, which didn't fit for my Macbook Pro is 221159039824

I hope this solves anyone's question in the future, as it was really a pain to find the right result.

Apparently these are called scissor clips and there are various types, identified as type A, B, C etc.

It's important you identify the type you need. To do this, use this handy reference

Full Product Page of Scissor Clips

I have a Unibody MacBook Pro early 2011, which is actually the first item on that page. What isn't immediately obvious is that if you click on the image, a new window opens up showing you images of the various scissor clips for the keyboards of the designated Mac products.

You can then double-check the type against the one you're replacing. So in my case, I can now confidently go ahead and order a bunch of type G standard clips.

I had expected there to be a link from that page to the product listing, but if there is, I can't see it. So instead, go to this page and choose your clips according to the type number you've now identified: SEE BELOW