I've been watching for some time for a better toolbox for my tractor. I can get just about everything I need in the OEM toolbox, but I have to take out a lot of stuff to get what I need, then figure out how to get it all back in there. I just needed a little more room.
I came across a small box made by Waterloo Industries in Missouri. It was $11 on Amazon. It has a removable tray inside and a metal locking latch. By my rough measurements, it has 67% more volume inside. There was a logo sticker on the front and a UPC sticker on the back. Both were removed easily with no residue.
Here's a side-by-side comparison with the OEM box:
The new box fits in the existing space without interfering with the backhoe or covering the storage area over the rear fender. I had to angle it slightly so that it would sit flat on the mounting plate (it has small plastic feet on the bottom). You can see the angle in the next photo by comparing to the wheel weight. If you didn't like the angle, you could cut off the feet or the plate.
I cut a piece of scrap outdoor carpeting for the bottom so that the bolt heads don't rub on the tools. I also mounted a waterproof pouch in the lid for my insurance card.
I use the removable tray to store my "wet work" stuff for hydraulic change-outs.
The tray sits nicely in the lid when you need stuff in the bottom.
The material in the new box is just a little less rigid than the OEM box. Also, the lid is not watertight. There are small openings where the handle connects to the lid. I'm going to add some silicon sealant in this area the next time I have a tube open.