Originally Posted by javabytes

Are you a Medallion? If so, search for a full Y fare and see which flights say Upgrade Available. You'll still have to call to confirm, because complimentary Medallion upgrades and miles/SWUs/regional upgrades are different inventory buckets... but a flight that has inventory for Medallion upgrades is likely to have availability for miles/certs too, so it can at least be a starting point.