A bit late, but, download the windoze driver package for the device, extract it and find the ".bin" file. Put this file /lib/firmware/ or /lib/hotplug/firmware/ depending on your driver. You may have to rename it. Check dmesg for the exact name of the missing firmware.
I use a DWL-120+ usb wireless, ti 1100b chipset, sounds like your using something similar.
Good luck.