I just picked up an excellent travel case from Office Depot, but I don't see it listed on their website so I don't know if it's either (a) brand new or (b) discontinued. Anyway, it's the Ativa Mobil-IT Ultimate Travel Essentials Netbook Caddy (what a mouthful of name)...
About the size of a portable DVD player case, it's very well padded and will hold your tablet plus power supply, cell phone, portable hdd, etc., etc., etc.