Air bags in rear of G sedan

[Road Ruler]

We tow a small camping trailer with our G sedan. Have a little sag in the rear of the car when hooked up. Want to keep everything level.

The air bag retailers have no listings for their products as one would suspect they don't think there would be a market.

Anyway I want to go this route and believe where there is a will there is a way.

Anyone retro fitted airbags in the rear coils on a G. If so I would like to here about it.

thnxs