Q: I'm looking for a Point of Sale receipt printer that supports Airprint

I haven't found any AirPrint-capable receipt printers. The Epson Mobilelink P60 series and the Star Micronics T300 will work over wi-fi, but not being AirPrint printers you'll have to find a third-party printing app that will work with them that would also work with your point-of-sale system. Epson has their own app, but I don't know about Star, though PrintCentral would probably work. The Epson now also says that it can print via Bluetooth:

https://pos.epson.com/products/MobilinkP60withBluetooth?ProductPK=679

It might be best to ask whoever developed the point-of-sale system you intend to use what they recommend.

Regards.