How to make homemade seat belt for your car?
Take an elastic belt and sow one end of it to the top portion your seat. Attach a clip on to the belt one the other end and attack another clip to the bottom side of the seat on the other side.
Take an rigid metallic chain and sow one end of it to the top portion your seat. Attach a clip on to the belt one the other end and attack another clip to the bottom side of the seat on the other side.