According to jhill :
I successfully replaced the bearings in my unit. Couldn't get them from the
manufacturer any more. Instead I pulled out one of them and took it to a
vacuum cleaner repair place, after a bit he found a pair that would fit.
Don't remember what they cost, but it was worthwhile --still using it 5
years later. But check the brushes, vac place may have replacements for
those too. Mine were still good.

Some of these bearings are relatively standard, so if there's a
bearing supplier near you, it'll be worth a visit once you've
checked them out and determined they're bad.

Bearing failures are often pretty obvious. Brush problems tend
to be high pitched screeches, whereas bearing problems are more
full-throated moderate-pitch howls.

[My skill saw's bearings are really badly worn, with a pretty
substantial wobble. It gets into a mode where the shaft
is obviously "orbiting" in the bearing. Resonant frequency
while the saw is stopping... First time I heard it, I practically
jumped out of my skin. Yeah, someday I should fix it. Sawing
interlocking pavers is bad for motors...]
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.