Help please

Hello ladies! Im a mother of 19month old I love trifting and estate sales, my husband doesn’t like to go out at all. So I go either in a bus or cab with my son’s car seat attached to a stroller base But now he is becoming big for car seat and not willing to sit. 1)Now how can I take him out (I don’t know driving) in bus or cab, which car seat is best for someone like me who is dependent on public transport 2)Also how can I make him sit without fussing coz if I release him he will crawl and he might break anything accidentally Ty in advance!!