It's been a long time since my kids have been out of car seats for some time. Hoping you can help me. We have a 7 month old 70lb puppy. Expecting him to be 90-100lbs full grown. He's horrible in the car. He can not relax. So I was thinking perhaps he needs the security of a seatbelt besides safer for all of us. So any recommendations that don't cost a lot.