I always assume that where a person finds a wandering iguana is close to the iguana owner's home. Make about 25 fliers with your word processor, and post them all around your location, up to 1/2 mile away. Someone who knows about that iguana will see the flier, and if it's a "wanted" iguana, the owners will contact you. If it's unwanted, this iguana is doomed. We here always have to remember that we can't save even 1/8th of one percent of the unwanteds.
You might have an iguana rescue operation close enough to you. Try to find an Iguana Society or an Iguana Rescue location. Ask the exotics vets in your area if they know of any rescue center.
BTW, lots of us believe that these Giant Green Iguanas should be much harder to acquire.
Someone, like SusanD, might respond with a list of iguana rescue centers across the US. There have been only a handful of them.