Although technically any printer that prints ZPL would work, we are currently recommending the Zebra ZP450, Bixolon, and Arkscan.
https://www.zebra.com/us/en/support-downloads/printers/desktop/zp450.html
Here are other printers that we have successfully connected with
Zebra ZP-505
Bixolon SRP 770 iii
Arkscan 2054A
Printers that DO NOT work
Rollo x1038
Zebra 2844
If you do a lot of shipping, you might be able to work with your UPS sales representative to acquire with technology credits. Otherwise, they are widely available on Amazon, ebay, etc.