I'm in the same situation... looking for DL MQM accruing Asia-U.S. flights on partner airlines. So, I thought I'd chime in on how I've been searching for specific fare buckets:

matrix.itasoftware.com
"Departing from" field: CAN :: ke+ / f bc=y|bc=s|bc=w|bc=i|bc=e|bc=l|bc=h|bc=t|bc=k|bc=m
"Destination" field: LAX :: ke+ / f bc=y|bc=s|bc=w|bc=i|bc=e|bc=l|bc=h|bc=t|bc=k|bc=m

The above searches all DL MQM accruing CAN-LAX flights on Korean Air.

Alternatively, www.travelzen.com is a good Asian search engine that shows all fare buckets (thanks, JieJie!).