Do a range scan and look for open port 515 and 9100. That will tell you which addresses belong to printers.
nmap -p 515,9100 192.168.1.1-200 -oG - | grep open
Then check for ports that are "Open". There is an
--open directive, but it's not working for me, for whatever reason.
515 is also used by print servers, so if you have a domain controller (or whatever) acting as a print server, it'll show up here as well. That's where checking 9100 comes in.
You can also just do
nmap -O 192.168.1.1/24 -oG - | grep printer and trust that nmap will correctly identify the device.