Try
www.ukfairs.net in Peterborough this Sunday.
I've bought severl 5.25" external caddies and installed 160GB drives in them. (Carrycopies of my desktop (3x160GB) with me when working away from home to use on my laptop (2x160GB & 18GB internal))
Caddies cost £23 each, and the drive costs depend on the size (£65 for 160GB) so if you only need a smaller drive then I'm sure you can cut the cost considerably