Gotcha. Maybe trays like this are a similar option (but with bottoms pre-installed):
Amazon - MTM 50 Round 12 Gauge Shotshell Tray (Black) - $6
They fit into cases like these two:
Amazon - MTM SF100D-09 Deluxe Case - $18
Amazon - MTM 100 Round 12 Gauge Shotshell Dry Box - $19
(I think that both of those cases include the trays, but the trays are probably good to use in other scenarios at that $6 price.)
Not nearly as convenient but a whole lot cooler is the Tesla Roadster - it holds about 6,600 18650 cells. 
Probably not what you had in mind though...
lol
Yeah, I know about those. Nice, but not enough storage. 
Crux is being insensitive to those of us who don’t have a storage solution for all our excess Teslas.
Here is another tray
3S150P?
3S50P
Because the trays stack!
As soon as I get dug out from all the snow I need to make a trip to Cabella’s