Here are some printable Post-It coupons. What is great is that they are in pdf format, which means you are not limited to the number of times you can print it. However, watch the expiration date as they do expire on September 6th!
$0.50/1 Post-It Flag Pack
$0.50/1 Post-It Sticky Note Pack
$1.00/1 Post-It Flag+Writing Tool Multi-pack