"Any designated deferred inspection location or CBP office located within an international airport should be able to assist you, regardless of where the actual document was issued."
there should be a CBP office in the port of entry at the airport. Actually, the officer at the port of entry is the CBP officer. For example, each time we enter US, the officer who isssue the I-94 duration to us is a CBP officer. So, you just go there and you should find the office.