Since you have someone maintain your mower and he didn't offer any DIY fixes, you're stuck.
However, if it were mine, I would turn down the worn area on a lathe and press bushings over it of the appropriate OD.
BTW - you didn't mention if the spindles were worn on the wheel side or axle/kingpin side. Either can be repaired if one has the time and experience.
Sometimes, there's enough stock in the wheel hub or the axle to bore it oversize and insert a bushing to take up the wear there.
jack vines