I purchased this https://www.amazon.com/gp/product/B003DKJQZE/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 and used a jigsaw to cut to size.
I can't see why you couldn't just drill your own holes and get the same result. I haven't had any crickets escaping.
I got my cham the kit from petsmart for his baby home. It was the 18X18X36 and I hand sprayed him until he moved to his big cage at 6 months old. I have the 24X24X48 dragon set up... I wish that huge atrium was out when I got Peter.
Pics of your set up when you're done?