Not saying horns are not good feeders but they grow at such alarming rate they will be way too big too feed to a chameleon that size. They can double and triple in size in a matter of days!
Fruit flies
small silkworms (gutloaded)
small crickets (gutloaded)
roach nymphs (gutloaded)
small butterworms (gutloaded or not)
small stick insects (gutloaded)
occassionally small superworms or mealworms (gutloaded)
small terrestrial isopods (gutloaded)