I picked up the flange and sleeve bushings mentioned in Ability to Repair: the Mower Wheel. The sleeve was easy to insert into the flange bushing using a bench vise. The flange was too wide to fit into a recess in the mower wheel.
right to repair
The rear wheel on my electric mower fell off. The mower is getting on but otherwise is still in working order - even the batteries take a usable charge. Each of the rear wheels has two ball bearings pressed into a 1.25" hole in the wheel which rolls on a 0.5" shaft. The inner bearing (lower right) was still intact but also failing.