Catch-22 problem

Catch-22 problem Good Cell and Poor Wifi or Poor Cell and Good WiFi your choice.

The TMO-G4AR Gateway performs well enough 80mips down / 10 up most hours of the day if the Gateway is in a Window.  I get a better performance with the Gateway on a 6 foot step ladder in my driveway and my laptop wired.  There is a design problem I get tolerable service with Gateway in my driveway but WiFi to the inside of my house it poor. I guess I could mount the Gateway on the roof with a plastic bag for weather protection and run an Ethernet cable to my own router.

Can anyone recommend an external mount antenna with 20 - 30 feet of cable for this TMO-G4AR Gateway.