Thank you all for your input. I have an Oregon, (one of the first versions available), and an eTrex 30. (In fact, I have about eight handheld GPS receivers because I used to teach "Map Interpretation and GPS" at my local community college.) I'll do some 'testing' with my 30, and if it does what I want, then I'll take a very close at the 35. Carrying a bag full of rechargable Enloops will take care of 'trashing the environment' issue.

Openstreetmaps is a very good resource. I have their data on most of my receivers, even the Edge 800. Openstreetmaps have 'saved my butt' more than once when wandering throughout Italy. Failing the above, then I'll go with the power packs that you guys recommended. In any case, there are options, and I thank you for making me aware of them.