Portable External Hardrive

I really need one an external portable hardrive.  I'm thinking of getting one with a minimum of 500GB or one Terabyte.  I have so many CDs, and DVDs with back ups.  I might just get two of them.  One for old data back up and one for new back ups.  I really want to get my stuff out of Tracy's laptop and back up Jamie's Toshiba laptop and do a complete system restore on her Laptop.  It runs slow and always running on 100% capacity.  I know its got to be a bug because of her downloads habit. 
I have two external hardrives but they are both bulky and need a power supply to work with.  I definitely want one without the need to plug into an outlet and very slim and compact.  Wish they had it in pink.  but black or dark grey will do.