LaCie is a known brand with large size external hard drives. You can also check out others at www.pricewatch.com. How many gigabytes are you talking about?
Since you are trying to back up your files from two laptop computer units, you really need to have or purchase a back up external hard disk drive with a high storage capacity, it would always depend on your budget. Try to maximize your budget for this device because it is very important to backup important files before it could be lost or stolen.