See links listed below for a comprehensive dive into getting better signal. Having a good, strong, and stable signal makes a world of difference in your LTE gateways performance and overall network performance.

Stores selling LTE accessories, devices, antennas, boosters:

Antenna Options:
https://shop.rfwel.com/4g-lte-antennas/?Ranking=Best__Seller&=&mode=6
https://www.wilsonamplifiers.com/
https://www.surecall.com/

Signal Booster Options:
https://www.ubersignal.com/ - https://www.ubersignal.com/cell-phone-signal-booster-guide
https://www.surecall.com/
https://www.wilsonamplifiers.com/

LTE Accessories/ Misc:
https://thewirelesshaven.com/