Car safety setup

I have a 16-20 lb range dog, and I’m trying to figure out what the safest setup is for taking him in the car.

Ideally I’m looking for two features:

1. A crash-tested seatbelt harness that hooks directly into the car seat belt.

2. Some kind of either booster seat, hammock like seat protector, or dog bed to go over the leather seat, etc that is compatible with the seatbelt mentioned above.

I don’t want him bouncing around and sitting directly on the leather car seats, but can’t see to figure out the right combination of products to both protect the car seat and also protect him. Thoughts? Again he’s 16 lbs, may get to 20, so he’s right above the threshold for Sleepypod and some other products.