The rechargeable won't hold a charge for the length of your trip? I often travel without a toothbrush charger, and the toothbrush will easily hold a charge for 10 uses.

On the other hand, I know the importance of having care-free gear [and you probably have other things to do besides testing battery charge shelf life].

Norelco used to make a AA battery powered trimmer. I own one. I'll be in your situation if I need to replace it. The decision to make the trimmer rechargeable was obviously made by someone with more power outlets in the bathroom than I have.... The AA batteries seem to last a couple of years between replacements, disappointing if the newer models have to be kept plugged in.