What printer can I use with my iPad?

You can use any printer that supports AirPrint. Here I found a few laser printers that are compatible with AirPrint https://www.thecrazybuyers.com/best-laser-printers/

https://www.imore.com/best-airprint-printers

In addition to nitin206's suggestions, many printer manufactures provide printing apps to connect their printers that do not have the AirPrint protocol built into the printer.