meb writes:

I've had some cones work themselves loose on a Dynacraft rear wheel
resulting in enough play to cause the dust cover under the freewheel
to get mangled. ... I was wondering is it possible to just cut a disc
from metal or plastic or cardboard of appropriate diameter to cover
the bearings ....

Maybe they aren't even necessary. If you regularly (like, every year)
grease the bearings, nothing bad will probably happen. I lost my
pedal dustcap in 1987. Nothing bad happened for 8 long years, despite
the exposed bearings.

- Don Gillies
San Diego, CA, USA