5G Signal Booster

I'd recommend looking more towards an external antenna myself.  T-Mobile does have devices with external antenna, and they're better at filtering/picking up a weak signal (in a certain direction), while a booster just amplifies all … including noise, and typically isn't directional.  Most companies are not in the business of 'boosting/amplifying' signal anymore, as they are not requiring carrier approval.

Como @iTinkeralot states - NaterTater has info, and has tested antenna for T-Mobile home internet devices.  The latest device also has ports for connetion.