overlay an image on product image in global product list


My goal is to create a custom field for a Product, called "hand made", which is a radio button "yes" or "no". If the seller selects "yes", I want that Product's image in the global product list to have a small badge (png) that says "hand made" - this would be an small image overlaid on top of the product image.

So far, I've used CustomPress to create my custom field for "hand made" yes or no..

I've also designed the badge (png) and have it ready.

How do I edit marketpress to check if a product is "hand made" and if it is, display the badge image over its product image in the global product list?