WLAN using USB modem and Ethernet wireless router.

I just want to get a little guidance if possible. I’m connected to Internet via a YISO S893v modem which is a wireless receiver for a cell phone signal and has only a USB port on the output to PC. I also have a WLAN in my house using a TrendNet wireless router. In order for it all to work, I have had to connect the modem directly to one of my desk top PC’s and use as a host, then bridge over to the RJ-45 output from my PC’s Ethernet adapter to the TrendNet Router. It’s working but the host PC must always be running.
I’d like to have the modem hooked directly to the router with a cloned MAC address but I haven’t been able to find a suitable USB to Ethernet converter for this. Anybody got any ideas?