I know you said no courses, but LSU Independent Study is self-paced, and the classes there are a bargain at about $250 each. They currently have two communication courses available:
LSU Independent Study Course List
CMST 2010 â Interpersonal Communication
CMST 2063 â Argumentation and Debate
BYU Independent study is also self-paced, and they have six communication courses available at about $423 each:
BYU Independent Study
TMA 150 â Public Speaking
COMMS 101 â Mass Communication and Society
COMMS 235 â Introduction to Public Relations
COMMS 300 â Media Ethics, Law, and Responsibility
COMMS 480 â Media Ethics and Moral Reasoning
M COM 320 â Communication in Organizational Settings
If you are determined to take an exam, the International Association of Administrative Professionals offers three upper level credits in Communications if you can pass their CAP exam:
ACE 2003
I didn't look into that very far, so I can't tell you when, where, or how much the exam is, but it does exist. It's the only exam I could find that hasn't already been mentioned.
Good luck!