Depends what size you want?
DELL-80/5-NB28 is the Product ID code for and 80gb one (replace the 80 with 40 for 40gb and 120 for 120gb). The actual drive is an internal - 2.5" - IDE - 5400 rpm - thats your search criteria or you can go upto 7200rpm.
Dell website has the 80gb one for £110 and the 40gb one for 96gb.
Whereas (as an example) Aria.co.uk have a 120gb Fujitsu one for £45 plus delivery
HERE