You have a 2018 model. I am not that familar with AS trailers built in the last 5 years or so. Below is true for older ones and I woudl think all Airstream trailer from 1967
Most Airstream shocks are mounted in a more or less horizontal position. There is no aftermarket shock made that is designed to be mounted in that type of position.
If there were, an air shock (or a much stiffer shock of any type) may do some damage to the shock mountings and/or the coach. An Airstream was designed to ride very smooth. Part of the reason for the smooth ride is the design. Design of the body mounting and design of the axle system. The design of the body is not a body on frame design it is modified monocoque design. Because of that the body "hangs" on the frame it doesn't ride on top of the frame.
So body movement is exaggerated from frame movement. In addition the axles with rubber torsion springs do a fair amount of dampening movement. In both directions. As such the shocks used only dampen a little bit more movement. And certainly not in a HD type of way.
The market place that Airstream sells against is a high end market. Generally users that do not go off road or into rugged conditions.
The only thing I could suggest is to tow slower.