I recently bought and used some from http://www.hfwilson.com . They are hardened and work great. I my case I mostly use 1/4", but they have 1/8", 3/16", 1/4", 5/16", and 3/8" available. You can get 3 packs, 10 packs, and 25 packs. Price is pretty reasonable. There 1/4" stock number is 06112 (3-pack). There phone number is 888-HFWILSON.
I have no affiliation with the company, just very happy to have purchased their bushings, and they work great! Thx.
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