Timbrens are the cheap and easy solution and they make them for the Raptor. But in order to control much sag, it seems you'd defeat the purpose of the Raptors soft, long travel suspension when not towing. If you have the truck for show, not go, then that's the economical solution.
Bags are the answer to maintian suspension performance when not towing though.
And they don't seem cost prohibitive if you can drop $60-70k on a pickup, basically for its suspension. I'd hate to give up what I paid 10 grand extra for, to save $1000 on accessories.
But to save money, can you just buy manual fill bags, considering you maybe won't be towing often? Only takes a couple minutes to air up before a trip.