Wireless printer

Hello!
I've a multifunction printer that i want to make wireless. Now it's
connected to a Printer server hardware, with RJ45, and it works, but
the scaner doesnt work in the clients if connected this way with the
Printer server in the middle.
If wired and connected to a simple hub, i now it will work. how can i
do be the same but in wireless way?
Can I connect a simple "usb wireless card" in the printers USB port to
do this? And the encription?
I think that i need something like a "Wireless hub", with no IP, to
make The net-printer and the clients talk directly.
Situation:
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I have got a HP 2820 (multifunction) laser printer. With ethernet
card.
I've got a router,in "infraestructure mode", wich does DCHP, to wired
clients and wireless clients.
The Wireless part of the LAN is encripted with WEP.
My printer is far from this router, I can only connect to it via
wireless
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Thanks in advance.
Urtzi