Hi David,
I just found this product:
https://www.iogear.com/product/GUWIP204/
Seems to do the wireless USB thing.
Also a better explanation of the wi-fi to serial device. I have attached a small picture to show how it's connected.
Between these two, should solve your issue.
Your limit will always be the wi-fi distance but you can also get wi-fi extenders.
Cheers,
Damien.