Wild Caught Desert Iguana HELP

I recently caught a wild Desert Iguana who seems sick. He let me walk right up to him and pick him up without a struggle. It was a warm, sunny day in mid-afternoon and he was warm to the touch, so not cold. He is very thin. He does seem to move well, when he moves. His eyes are bright, nose is clear, no audible breathing. No obvious load of mites. Has not had a bowel movement yet, but I do intend to deworm him.
So, I keep a pair of uromastyx, and live and grew up in Desert Iguana territory, so I'm not too concerned about tank set up and care. What I'm really concerned on is diet and getting him to transition from his wild, native foods to leafy greens, vegetables and seeds that I provide my uros. Does anyone have any experience or suggestions? I can provide him with native collected leaves and flowers, but I would prefer to get him to switch over (at least partly) as soon as possible. Obviously, because he is so thin, I also don't want him to miss too many meals. Open to any and all suggestions.
Thanks!
Also: He was legally collected