What's stopping Purdue Global from having labor representation, especially if labor and management can work together on educational quality? There are several unions that represent instructors and staff. It's illegal to fire a person for trying to organize, but that doesn't mean that it's not without stress and the threat of being fired.
You could try SEIU (Faculty Forward), AFT, AAUP, UAW.
There are also adjunct groups.
Con Job: Stories of Adjunct and Contingent Faculty
Adjunct Nation on Twitter
Coalition of Contingent Academic Labor
New Faculty Majority