Member POSDAKOTA turned me onto a link to ebay about a year ago.
I got the valve covers for IIRC $80.00 and the Breathers for $30.00, Killer deal on them.
I recommend using a cork valve cover gasket with these valve covers. I had another set not polished that leaked like a garden hose on Brians Dyno after about 5 minutes of run time. The rails sometimes are not totally straight. The cork is squishy and takes up the gap. FYI