I have done this in the past with guys that I have had to put on COD.
Tell the guy that you are going to raise his prices 10%, and keep track of his debt. Send him an email after each sale, and tell him how much he owes.
Hey "Bob" after this shipment, you only owe me $57,000.
Hey "Bob" after this order you only owe me $51,000.
Worked for me. He is now all paid up.
