What is this plate called?

[Mr Bob]

What is the metal PCI plates in the back of your case that covers up unused PCI slots called?

Where do I buy them?

See http://ask.creative.com/wwimag...l_hardware_install.jpg as an example (the grey plate right below the black arrow).

 

[Rubycon]

Blank expansion slot cover...

They are cheap

You may find a pc builder that will give them away as well.

 

[Zap]

Slot bracket?

I suggest going to a local computer repair shop to see if they'd be willing to unload some to you for next to nothing. At the computer store I used to own, I'd give away stuff like that (extra screws, motherboard standoffs, slot brackets) if anyone needed them.