Feeder insects are a poor source of Vitamin A no matter what you gut load them with. Crickets have no livers which is where it is stored. To be honest, from what I've read on Vitamin A content of insects, I am not sure how they get it in the wild unless wild insects are much richer in Vitamin A than the insects we feed in captivity.
@guanagator I'm hesitant to comment because there is a risk of an overdose, plus there are other vitamins like Vitamin E that should be supplemented in conjunction to Vitamin A. I wouldn't suggest giving a full gel cap to a chameleon without knowing the correct dosage to treat vitamin A deficiency. I want to buy injectible Vitamin A and inject feeders, but keep forgetting to ask the vet if they will sell me some. I can say that vitamins do deteriorate quickly in an opened bottle. I keep mine in the fridge and discard
.