In my experience, Flashbangs aren't used nearly as often as other weaponry. Or even, grenades altogether. Science/Chemistry tend to do that and occasionally give us a couple, if any.
I will note that, with my Box and some of the base supplies from one Locker, I end up restricted to one spare slot in my backpack/satchel.
This is using a slot for my Helmet, Box, the Sec gasmask, putting my Taser away in favor of the baton, shuffling cuffs and flashes and internals around, and a crowbar. screw your power outages, i want to arrest stuff
Personally, i'm in favor of an extra slot somewhere (like the chest carrier), and/or shrinking the mask to fit in boxes (or adding more duffelbags to the Sec wardrobe lockers).