Walmart offers the Radio Flyer Moto Racer 6-Volt Battery Operated Ride-On, model no. 903, for $39.97. Opt for in-store pickup to dodge the $5.97 shipping charge. That's the lowest price we could find by $14. It features a rechargeable battery, push-start button, and 7.5" grip tread tires.
Walmart offers the Radio Flyer Classic Walker Wagon, model no. 612, for $45.20 with free shipping. (Amazon charges the same for Prime members; Jet.com also has it at this price.) That's the lowest total price we could find by $11. It features removable wooden sides plus a front bumper, and provides resistance to help with walking.
Note: Select Target retail locations offer it for $42.34.