Here are some links to PDF resources I have found thus far:
Congressional Resource Service:
US-China Relations: Policy Issues
China's Holdings of U.S. Securities: Implications for the U.S. Economy
The CATO Institute:
The Debt Threat: A Risk to US-China Relations
The New York Times:
China’s Treasury Holdings Make U.S. Woes Its Own
And here is the link to the Public Forum Search Engine.
UPDATE:
The Only Useful thing I've found from the Treasury:
Major Foreign Holders of Treasury Securities
The Congressional Research Service (Again):
US-China Trade Issues
