Got a bike path along a river trail to downtown, maybe 1 or 2 hours bike ride.
Been specing out electric battery assist. Maximum battery cell hiding maybe inside hollow tube frame, if possible.
Downside to electric, 120v is slow charging. 220v or 440v is required for quick charge. But if you ride downtown, there are no higher voltage outlets available.
There may already be a pedal assisted bike available with the range you need, if not, couldn't you get a extra battery, leave it to charge at some location in town? Perhaps a service station or garage might be willing to work with you on something like that for a nominal fee?
You could then just swap out batteries for the trip back.