Nothing better IMO than having your wife along for the ride. Fortunately/unfortunately my wife doesn't need "e" power to keep up (we ride un-electrified on weekends and one night during the week). There are many options, both DIY and OEM. Tell us the requirements and we can provide more assistance. In general, if the terrain isn't hilly a hub system as above will suffice; otherwise a mid-drive may be indicated. Look at the thread "DIY Systems" as well as others in the forum for ideas.