In addition to being the webmaster for the Armed Guard / Merchant Marine website, I am a member of Project Liberty Ship, which owns and operates SS JOHN W. BROWN, one of two surviving, operational World War II Liberty ships. (CHIEF OSCEOLA, in which your father served, was a Liberty ship.) I am also a member of JOHN W. BROWN's volunteer operating crew.
We have a Ship's Store aboard JOHN W. BROWN that offers for sale Armed Guard patches and ball caps. See http://www.ssjohnwbrown.org/ship-store/patches for patches (there are two Armed Guard patches, the third and fourth in the top row of thumbnail pictures, $5 each plus shipping and handling), and http://www.ssjohnwbrown.org/ship-store/baseball-caps for ball caps (again two Armed Guard versions, the last one in the top row and the first in the second row, $25 each).
Ron Carlson, Webmaster
Armed Guard / Merchant Marine website