Air bags would be a good solution, but before you spend the $$$$, check to make sure you are lifting sufficiently with the spring bars.
I use 1200 lbs rated spring bars with my setup. First, with the truck on level ground, I took a measurement from the ground to the bottom of the hitch receiver. Then I set the trailer on the hitch , full weight, and measured again. After fooling with the spring bars for a while, I ended up with the rear 1" lower than the original measurement (empty), and all is well. It has sufficient weight on the rear for traction. Its all in the spring bars adjustment and having heavy enough spring bars to lift the truck without having excessive bow in the bars. After all the tweaking and measuring, I found no need for air bags. Hope this helps.
