At first glance, this Grabinet Outfitter Kit appears useful. It's a set of nine drawers that apparently allow you to store/organize smaller items in a milk crate.

The catch is, these won't fit in a standard milk crate, just the ones by its manufacturer, UbeCube. (Standard milk crates are 11" tall and 13" square. UbeCube's offerings are slightly larger, and truly cubical at 13.5" all around.)

I poked around to see if anyone makes a similar offering for actual milk crates. The Grip Store—that's "grip" as in film set, not hand traction--makes these $10 dividers for standard milk crates used by the dairy industry (and apparently film production crews). Each unit consists of two plugs that snap into the crisscross lattice on the sides, and a divider that slots between them. The divider is only as high as the bottom of the handle cutouts, so you can still pick the whole thing up.

Print Foundry, a 3D-printing operation out of Fargo, North Dakota, sells just the plugs, four for $13; you supply the 1/4"- or 6mm-thick divider of your choice. The company is a mom-and-pop outfit, and it shows in the finish quality of the product.

What I could not find is anyone who makes a drawer-style offering like UbeCube's. There's either a gap in the market, or no market at all—after all, the type of people who use milk crates for storage tend to be DIY'ers who will improvise their own solutions. As evinced on Pinterest.