Hi
You will not be able to use the WAN connection : that is only to connect to the Internet.
Check if your router can be setup in client mode. This way you can simply connect your printer and other devices on the lan outputs. You should disable the DHCP server to avoid any conflict on the network.
If you are unable to setup your current router in Client mode you can look at travel routers. All of them are able to do so. If you need one with 2 lan ports you can refer to this model :