Depends on the volume and use.
You could try dipping into pu varnish.
Quick, cheap and strong.
But, longer drying time as thicker coverage.
Usually when I work on projects, I work with clients to modify designs to suit the required task - makes it much easier for everyone. As an example, you could have an indent die made to press the design into the tag - but obviously that depends on client and use case. The issue in your case would arrise from material compatability - the more materials you use, the more failure modes you expose. Simplicity is your friend. What happens when your metal tag gets hot/cold?