A heat rock is exactly that - a rock with an electric heating element inside it. You plug it in, it becomes a warm rock.
He would also need an enclosure he can climb in (I
actually re-fitted a twin-over-twin bunk bed with shelves, branches, flooring, screening and doors. And, special heat lamps, and lamps that produce something akin to natural sunlight. The room was kept at approximately 75-85 degrees year round (yes, the iguana had his own room). All the lights and heat elements were on timers.

What is the point of rules that are not enforced?