Lookup safco flat files. I got one used literally last night off craigslist for $100. SUPER deal. I am flush with storage now.
Mine is 5 drawers at 36”x48”. Yeah, 3x4 FEET. It’s not a small unit for sure.
This one is like it, albeit smaller and far more expensive since it’s new:
You can find them used in most cities because architectural firms frequently sell old ones.