I'll be changing cars soon to a 4-door sedan that won't fit a crate (wah, I love car crates!), so I'm looking into seat belts. But there are so many different ones. Is there something I should be looking for? I've also seen some just have a very small leash type thing that the handle just slips onto the seat belt then you latch it, which makes me think I could just get a small leash (like a foot or two) and then get a nice harness. Suggestions?