What are y’all using for a large but portable cleaning supply tool box? I’ve got ARs in 4 different calibers plus 9mm, 22LR, .308 etc. I want something with enough capacity to divide up brushes and patches by caliber.  

I was thinking one of the modular options from Milwaukee? Anyone got anything better?

either that or look at what some crafters use to keep all of the items they use in order. I have a large box with removable plastic drawers that are stand alone covered segmented trays that I use for gun parts with one tray for each platform.

it doesn't look like it is available anymore but this is it. There are lots more from companies like Akro that make plastic molded stuff.

Fishing tackle box for decades!

https://www.planooutdoors.com/guide-series-tray-tackle-box-1592620

Mine is similar to the above link.

Tackle boxes are the best bet

I use one of the flat DeWalt boxes from Home Depot. The pull down compartments work great.

a moderate size fishing tackle box is all you need.

I have a small plastic tool box for pistol cleaning tools/patches and another for rifle related stuff.

I just use a sectional plastic handled cleaning tray holder with some MTM brush containers for the brushes and small plastic bags parts came in for the different size patches. One sectional part holds the oils and cleaning solvent bottles and the other side long sectional one holds the cleaning rods and the rest of the miscellaneous stuff.
The MTM brush containers https://mtmcase-gard.com/products/jag-n-brush-case-4-compartments kind of are the key to making it work. I wrote on the outside of the brush containers what brush size was in each section.

I have a work bench just for guns and I have the supplies in the drawers.

Though this post makes me want to find some plastic dividers.

Tackle box FTW

Same, flat box, clear cover, stackable. Holds tools, parts, etc. Mobile armorer's kit.

I've been using this. It works well enough for me. I do wish it was just slightly bigger. But it's nice and compact.

https://www.amazon.com/gp/aw/d/B07YF96WFG?psc=1&ref=ppx_pop_mob_b_asin_title

This

I have a Large Plastic Tool Box with Tray. I have short sections of PVC Pipe epoxied to the bottom along one side to hold pill bottles with different size patch's, Hoppes #9, a Lucus Oil Bottle, and a small tub with grease. I have plastic Cleaning Brush Box's in 204 Ruger, 22 RF, 5.56, 6.5mm, and 30 Cal to hold Jags and Brushed for 204 Ruger, 22 RF, 5.56, 6.5 Grendel, and 300 Ham'r. I also have Possum Hollow AR15 Bore Guides for all the above. Note my 6.5 Grendel Bore Guide works fine for 22 ARC. I also keep Brass Loop Handle Pistol Rods to clean the chamber area. I keep Rubber Gloves to keep chemicals off my hands, and paper towels to wipe rods etc. in the box. I also keep a Sinclair Action Link in the box to hold the upper open for cleaning.
My box evolves as I find better ways of doing things. An example is my Hoppes #9 Jar. While at the convenience store I spotted a small Fruit Jar with some sort of moon shine in it. It has a big lid the right size to dip patch's. I keep it refilled from my big Hoppes bottle.

I have started cleaning before leaving the Range. That way it gets done. If I take a gun home dirty I will end up getting side tracked, and it does not get cleaned.  Cleaning as part of the Range Trip is a very good policy. The wife appreciates my not stinking up the house with Hoppes also. My view of how Hoppes smells and hers is different.

I also have a second cleaning box set up the exact same way for my Single Shot Hunting Handguns.

My Bolt Rifles have been neglected lately. I plan to start working with them again this Summer. I plan to put together a third cleaning box for them as well.

Bob R