I like this trash bag it fits the bill for me pretty well.  Just about the right size bag I'm not sure I would want it any bigger,I think it would get in your passengers way as they get in and out.  I really like the elastic closure on the top if it does get bumped nothing spills out.  Its also really easy to empty with the velcro along the bottom.  I use this in my work car and I am going to purchase another for my personal car.