Hard disks today are better engineered than some of the old ones. Thats not to say they're failsafe (in fact because they're more tollerant to bumps, we abuse them more these days).

You say you have 3-4Gb of data - thats good - but remember data does tend to expand, and not shrink.

So its down to Bus Powered Hard disks, or a 8/16Gb Pen Drive (memory stick).

Advantages of Hard disks are that you can store a lot more data. One nasty bounce on the floor, and its game ovr.
Advatngage of a Flash Drive - Faster, smaller. However, they can still be crushed (which is fun to see when your Director crushes one in front of you), and the cost can be silly at higher capacties. (also much more loosable)

Hard disk brands:
LaCie - they do ruggerised hard disks http://www.lacie.com/uk/products/range.htm?id=10036
WD Passport - Slim Harddisks - http://www.westerndigital.com/en/pro...sp?DriveID=317

PenDrives - I recommend the Corsair Flash Voyager Pen drives http://www.corsair.com/products/voyager.aspx - efficient, and i've had not had one pop on me or my users yet.

As always, take care of your equipment, and your equipment will look after itself!