There are multiple way that you can achive your goal, you can buy a Wireless print server something like a Linksys WPS54G Wireless-G Print Server, USB 2.0, you should be able to google that and find it.
You can go to Tigerdirect.com and type in Wireless print server and you will get quite a few hits.
Or you can get a wireless router if you do not already have one that has the capabilities to connect a USB device.
You might also want to call Lexmark and find out if they make a wireless card for your printer, I know that they make them I just do not know if they make them for your printer model.
Hope this helps.