In article et,
says...
You should be able to buy these in quantity. check with www.mcmaster.com
www.mscdirect.com or google away.

Search on 'bushing', 'sleeve bearing', or 'standoff'

I looked through McMaster, found SAE 841 bronze sleeve bearings for $.62
each part number 6391k178. They have the same thing in steel, just not
quite the right wall thickness.

SAE 841, aka Oilite, is a sintered bronze and will not hold threads very
well. SAE 660 bronze is also very common and would be a better choice in
this case.

See the bottom of McMmaster page 1018 for steel bushings.

Misumi America is another possible source.
http://www.misumiamerica.com/

Ned Simmons