thats a crock, no offense. If I told AZ Commercial that the fuel line O-ring for my 01 ram 5.9l was missing and I needed it, they'd go pull the damn fuel line or call around the state to have someone pull the line and check the O-ring.
As a single person you don't have as much pull, but you can ask them to size one off their own line, most of the time they will. Or hell, just buy the line, open it in the store, pull the O-ring out and ask them to find you another, then return the line with the original O-ring.
Sorry, I don't know what the O-ring size is.