Pair of rear air bags from Lexus at partsouq.com are less than $400 shipped to your house.
I’m sure you can find a local Indy shop to replace for $300 labor.
48090-35011 Rear LH $150
48080-35011 Rear RH $150
Plus shipping from outside the county $78
I ordered lots of parts from them...
Maybe you need to play with the shock settings. Move the dial to comfort and see if the shocks get smoother…or move it to sport to see if they get stiff