Thanks so much @Eelman and @WarrenBelz for solving this for me. You guys are awesome! This will help me in other apps as well.
// clear colLeaders first, for obvious reasons
// collect into colLeaders a table of names and IDs
// here, I've used my SP ID column but you use your relevant OrgID column name
// Use GroupBy to build the Leaders collection with their assigned OrgIDs
// Unfortunately you can't use GroupBy directly on your SP list due to delegation issues, however,