Yes, they don't work as well as the ones you attach to a router but you can get one. Usually the carrier gives them for free, in this case you can buy one from eBay or something
It usually comes with two units One you put where the signal is good and second where it needs a boost
The one I just got from T-Mobile was 2 pieces, one placed by the window and one in the room ,or rather on another floor in a room, as far apart in the home they suggested, and all I did was plug then into the outlet and that's about it.
Sometimes they recommend you to call the carrier and register the phone with the booster.