I use these containers

https://www.amazon.com/dp/B00CQGTGZQ/ref=cm_sw_r_api_i_QQZZBZBDR6RT9QZTYFZ0_3?psc=1

I'm a cheap bastard and instead use varying sizes of these that I can pick up very cheaply at local home goods stores (Target, Walmart, etc). Get a roll or two of non-skid plastic liner meant for cabinets and you've got a stackable storage option that your models won't slip in.

I find things like specially made army bags are far too expensive for what you get.