Airbag Suspension Options Ford Expedition

I purchased a 2017 Ford Expedition XLT new. I knew it was sag a bit in the tail end before I purchased it, despite being appropriately connected to a weight distribution hitch. I figured I would have airbags installed, as some friends have recently shared their positive experiences with me. My local off-road center informed me that there is nothing in the books for a 2017 Expedition for air suspension support. I called both Firestone and Airlift directly, but neither have options available. Any suggestions? Is anybody using any other options? I don't want the rear-end permanently elevated, as our tow miles will only account to about 2% of our total miles to be driven. I look forward to and appreciate any feedback.