I would make 100 leaflets and distribute them in a one mile radius near your present home.
If you live where it's not too cold to do this, showcase your ig near the sidewalk at your home. Hold him on your lap, and show him off in the cage. You have to be with him with no breaks He has to go everywhere you do, to avoid theft. To go inside for two minutes, the show cage must be easy to carry. If your neighborhood doesn't produce a new owner, go farther away and do it again, even to another city. Be sure to ask every exotics vet in your state to hang one of your fliers.
Your main problem will be how to know if the prospective new owner knows enough, and makes enough money to be able to afford the typical iguana vet bills. If you give it for free, you might attract some sociopath to adopt him just for dinner, with the ig as the main course.
So, IMO, you must charge some money as a hedge against dishonest adopters. That way you remove any possible gain the adopter may have in mind.