I'm going to be recording many hours of footage while outdoors, without a laptop. I'm wondering if there is a portable hard drive or way of recording 20+ hours of footage. I am using a Canon XL2. Any suggestions? Thanks.

Look out for the Firestore. But be prepared to bleed money.

Are you sure you can't borrow a laptop from a friend or something? It would by far be the cheapest solution; all the small portable solutions I've seen offer little disk space for ridiculous amounts of money.