Walk behind REAR wheels for 21" T-B fwd

REAR (non-drive) wheels are wobbly & about to fall off. Online price is $40 each (!!!) Stupid plastic bearings. Can real metal bearings/bushings be used? Or, is there another mfg. whose wheels aren't so darned expensive?

12AV566N011 - 2007 - FRONT self propelled - 21"

Searched this site - didn't find anything - yet.

Thanks!