Here are a couple of places that sell tiny fonts. Although you can use the resize option in your embroidery software, I find that if you want the really small versions it's best to purchase a font that is digitized to that small size:
http://www.sew-n-2-u.com/shopdisplay...cat=Tiny+Fonts
https://www.theitch2stitch.com/Teeny...dery-Font.html
As mentioned, don't use your usual 40wt embroidery thread, go with a 50 or 60. Also, be aware that although these are listed as fonts, they are actually individual embroidery designs, one for each letter. You need to have some embroidery software to pull the individual designs in. The first label takes the longest. Save it & just edit it for future labels.