After years of fussing with tackle-boxes and the like, and a few months of fruitless search for something that was exactly what I wanted, I finally just built my own kit. I put a little hardware drawer thing on one end (for all the little bits & bobs), three large pockets on the other end for larger objects (first aid kit, spare T shirts, pencil bags etc.), and elastic down both sides to hold long thin objects (scale rule, three hole punch, as shown).
It's a smidge heavy, but holds exactly what I need in ways that are super easy to access. It's even broad enough to tuck my three ring binders on top, between the carry straps, when moving to different spaces.
I heartily recommend sitting down and thinking about exactly how you want to use your kit, and trying to find a container that fits those qualifications. And if you can't find it, build it! (or make friendly with your TD and beg them to build it!)