Anthony wrote in
:

Check with some of the extrusion manufacturers, i.e. Bosch, 80/20,
FlexLink, etc. They offer plastic covers for the T-Slots in the
extrusions, maybe you can find one that will work on the mill slots.
These will be in a double-leg T or square U, with little lips on the
ends of the legs to hook into the T

A cheap alternative are the T type aluminum pieces that are used in drop
ceilings. They can be cut easily and can be found in most dumpsters or
landfills.

Geesh, I'm startin to sound like Gunner now. But, hey if its free its for
me!

Bing