If you like what you see here, consider leaving a tip.

Use this slim key fob to label your keys or make a backup of an ID card.

Instructions:

Print out the key fob frame and label retainer, and make sure the retainer fits in the frame. You may need to resize the retainer model before printing to get a good fit.
There are many web sites you can use to create a barcode. I used TEC-IT.com to create a code-39 barcode to match my rock climbing gym member ship.
Download the barcode image and open it in an image editor. I use GIMP. If you don't want to keep the characters on the bottom of the image, crop them off and resize the image.
Barcodes need some white space before and after the image. A width of 34mm leaves about 3mm of white space before and after. To get the best quality printed image, set the image resolution to your printer's highest capable resolution, then print the barcode making sure to select your printers highest quality black & white setting.
With your label printed, trim it slightly smaller than the inside dimensions of the key fob frame.
I recommend laminating the paper with clear packing tape to give it some protection from water.
Test fit the label in the frame and make sure the retainer piece fits inside before gluing the retainer in place. Trimming the corners of the label can help with fitment. I like to use a slow cure two part epoxy for bonding 3D printed parts. A 30 minute working time is usually more than enough. Only a small amount of glue is needed to keep the retainer in place. A tooth pick would work well for applying the glue.
With the retainer in place, lay the frame face down on some waxed paper and place a flat weight on top and let the glue cure.
When the glue is cured, remove the weight and place the fob on a key ring. You're done!

Found 2 3D-models for “id key tag” across many websites

Barcode Key Fob

KEY_NUMBER_PLATE Schlüsselmarke mit Nummer 001 - 150