Thank you for your inquiry.
There is a U.S. Navy Armed Guard and Merchant Marine Museum in Vero Beach, FL. They may have information on how to obtain a Navy Armed Guard flag. The museum has a Facebook page at https://www.facebook.com/USNavyArmedGuardandMerchantMarine with contact information. You might also telephone Capt. Richard Martucci, who is affiliated with the museum and with whom I am acquainted, at 772-559-1946. Tell him I sent you. As far as I know the museum does not have a website.
I trust the Ohio Veterans Memorial Park includes a U.S. Merchant Marine flag, which is somewhat easier to obtain. The Armed Guard and the Merchant Marine were literally in the same boat during the war and the Merchant Marine deserves the same recognition as the Armed Guard and the rest of the military.
Ron Carlson, Webmaster
Armed Guard / Merchant Marine website