Personally, I think the best (and most economical) way to get the message across would be to add a cardboard hanger that can hang off the slightly unzipped big front pocket. It’s no different than how a wallet sitting on display will show fake credit cards, etc. to show what each section is capable of holding. (forgive the crude creative representation!)
The printed, die-cut piece would look something like:
And on display would look something like:
What do you think? I like that you get the visual pop right away. Way to think outside the tag Barney!