Get your self a piece of banana or even just any old fruit..put it in a cup...that you can cover,stick it outside...wait............You just maybe surprised!!!!!
It is great what you want to do, but rescuing a possibility very fragile animal from a questionable pet store is only going to support that store,and encourage them to purchase more for sale....hate to be so negative...but this happens all the time....buy from a more reliable source...
For what its worth...its not a great idea to leave a bunch of crickets running around the cage...they do bite...and a lot of them will tend to "freak-out" most chameleons...
I've got some 3/4" insulated boxes if you need...local pick-up only!!! I get my cups from"smart and final"..the cloth vented insect lids ,that work great with the cups for shipping and for raising fruit flys,at "superior shipping"...