There are herpetological societies around the country which could be used as source contacts to find herp educators. Information on most states, and on specialty societies, can be found linked to my Herp Society page. There is a Petco person in the northeastern U.S. who puts on talks at store openings, including, we were told, bringing large iguanas. This includes some tortoises, pythons and boas, iguanas, and Nile monitors. Iguana tails range from 2.5-3 x the svl.
Females are generally smaller than males.
Perhaps a better resource to draw on for public lecturers would be reptile rescue groups. I have offered to put together a sort of syllabus based on the lectures I do, if indeed there is any real interest on Petco's part in my actually doing so. Petco isn't selling large enough enclosures. NO store is currently selling appropriately sized and designed enclosures suitable for large reptiles. Petco said that they will be phasing out the sales of green iguanas, instead replacing them with more appropriate lizards, such as leopard geckos and bearded dragons.