[UK] where do I find Ergotron arms for cheap? (Or any arms like them) [UK]

[wajed]

On Amazon.com they are about $110, but on Amazon.co.uk they are about 110 pounds; that's a huge difference.

So, any suggestions?

I'm looking for this: Ergotron LX Desk Mount, or a similar one.

EDIT: Actually I may not be able to use this one, please suggest anyone that can be used without making holes, or having to hook it at the back of a desk (because I can't do so: no space for the hook)