Search Amazon, etc. for "gps data logger". You'll find units under $100 the size of a pack of gum, fits in jersey pocket, run all day on internal battery, then d/l data later. Something like the Garmin units makes sense if you want bike computer, HRM, and nav (depending on model) functions in one unit.

While not a data logger, I have a wireless (blue tooth) Holux GPS receiver that does the GPS reception quite well. I used it with my Nokia 800 palmtop as a GPS logger, stopped only because the Nokia and my regular phone and the GPS were more than I wanted to carry on a ride. A smart phone with b/t (external GPS) or internal GPS and an app to log the GPS data would let you do the same thing. Didn't get a logging version at the time as I wasn't thinking of using it that way; should have.