I had a chat with my nephew, who is in similar situations like you (near Sullia). According to him, signal boosters are not available due to supply issue.
He has resorts to Beetel F5 router /phone with external antenna and has found better results. Again, it supports only one SIM and does not fit your complete need. Huawei B310 is better but doesn't have antenna connectivity. Going for a device, which can connect to antenna is better. Yagi antenna will yield better results is my thoughts.