Picked a couple of these up today from my local Tesco. A bit larger than most 4.3" satnavs I had an inkling these might just accommodate my 2.5" portable hard drives and they do. There was even enough room for the usb cable.
The case is not recessed inside; instead the material covered sponge interior gives way to fit very snugly around any object you place inside, so that even smaller objects won't rattle about.
This proved to be a perfect fit for my WD elements drive and much cheaper than the usual Case Logic hard drive cases you get from PC World. For some strange reason known to Tesco, the Technika 3.5" case was £9.95 instore although discounted on the website.
You can also use this for your satnav. If you must.
Case Type Hard
Features of Product Strong protective carry case for 4.3" sat navs
Product Depth 4.4 cm
Product Height 11.3 cm
Product Width 15.3 cm
Shoulder Strap No
Water Resistent No