I've made my own for years by purchasing gym bags. Found out a while back that many of the zipper pockets on these bags are exactly sized to hold 3600 boxes, some are for smaller boxes as well, some even for the 3700 size. It's like they measured for it when they fitted them.
The one I have now holds quite a few of the 3700 sized boxes (3701's are thinner, more adjustable with smaller available spaces internally, and are awesome for crankbaits, no wasted space, each in it's own spot, get more boxes in the bag this way too). I also have 1 of the 3600s in it's own zipper pocket on the front outside the main bag. The two vertical pockets, one on each end, would also each hold a 3600 as well but I use these spaces to put soft plastics in their own pouches in. Holds a good dozen or more bags per side so I have nearly 30 types of worms, lizards, and craws with me at any one given time. The main compartment of the bag is so stuffed with boxes that the last space at the top is not usable to insert just one more box due to the fact that the box is wider than the opening and needs to be inserted and manuvered to lay flat (I don't stand them up, too much tangling of hooks that way). So to overcome this, I just put three 3500s side by side, one in at a time and filled it to full capacity this way since I can put smaller ones in and slide them back under the fabric and then pop the last one in right in the middle. Zipped up there is absolutely zero room for any movement of boxes to shuffle around. 3500s work well to hold hooks and sinkers, swivels, things like this where if you spill them you don't spill a lot since the box is too small to hold much. This system could not be more perfect.
When I beat the bank, I have a shoulder strap for carrying this rig. When I go on the boat it is perfect to carry everything compactly but easily reachable. Other things it has are places outside to strap a 20 oz. drink bottle to, or cell phone pocket, stuff like that. I paid $20 for it total, but I already had the boxes. They don't cost much to purchase one at a time when needed and I've had them for years so when the bag wears out, another $20 and I'm good for a few more years.