I've heard a lot of good stuff about Wingnut packs, they're a compromise between a backpack and a *ahem* lower-back pack, but they're not cheap.
http://www.bikeradar.com/gear/category/ ... 3-11-39743
(as an aside, yes we call them Bum Bags in the UK and I understand that in the States they're called Fanny packs; in the UK, the fanny is round the front, and only on women, so when we group of Brits were in Wyoming and overheard a guy taking a photo of his family and asking them to smile by saying "OK everyone, say fanny farts!" we knew it sounded perfectly innocent to him, but we couldn't help but fall about laughing!)
http://www.bikeradar.com/gear/category/ ... 3-11-39743
(as an aside, yes we call them Bum Bags in the UK and I understand that in the States they're called Fanny packs; in the UK, the fanny is round the front, and only on women, so when we group of Brits were in Wyoming and overheard a guy taking a photo of his family and asking them to smile by saying "OK everyone, say fanny farts!" we knew it sounded perfectly innocent to him, but we couldn't help but fall about laughing!)