Add sold out banner to sold out products on website

We have a Wordpress e-commerce site with Woocommerce. When a product is sold out, we'd like there to be a banner in the top left of the product box on the home page and on the product detail page that says SOLD OUT. We already have the image made; it's just a matter of adding a simple conditional statement that checks whether the product is sold out and, if so, adds the img in the right spots. There is code elsewhere on the page that checks to see if the product is sold out and, if so, outputs something else, so you should be able to just adapt that code. This should take 5 minutes and cost $10. The only complication is that the site is live, so you will need to be 100% certain your code is flawless before uploading it.