If you are using a Brooks saddle you might want to try a saddle bag like the ones listed here:
http://www.rivbike.com/webalog/baggage_racks/ or here: http://www.wallbike.com/berthoud/berthoudbags.htm. I tried them once and liked them but one thing you have to get used to use your hamstrings touching the bags. At least that was the case on the one I tried. I did a one day overnight tour using my camelback and worked well even w/ a pair of teva's inside so your small pack would probably be OK. Assuming you will be credit card touring?