assuming oem parts are unavailable?
are they missing, damaged, wore out?
is it a plain wheel/tire or does the drive mechanism engage some sort of gear teeth or keyways in the hub of the wheel?
if wheel is plain, several places sell steel or plastic wheel/tires by tire diameter, width, and axle diameter. you make get lucky for a match.
if wheel is unique to drive system, you may find nos parts by oem number on internet market sites or longshot might find aftermarket for specific model.
if nothing compatible readily available, local small engine shops may have replacement or repair solutions with minor modifications to available wheels.
I never knew they made push mowers so not sure how big market is. good luck!
