One way of doing this could be to add a label to your product image. Something like this -
There are apps on Shopify that allow you to easily add your labels to your store. You can check some styles here.
In case you want something custom, you can always reach out to me. My team can help put together the design that you want - you can share the example if needed. And it can get added to the sticker library.
Using the app is fairly simple - pick your product, select the sticker and just hit apply changes. Saves a lot of development effort.
You can ping me if this would work for you.