Here is another toolbox option. I also lamented the lack of a handy toolbox on my BX2660 and was very interested to see the options posted on this forum. Good ideas can lead to other ideas, and while this one may not suit all BX tractors (eg would not suit those with a rear mounted excavator), it should be ideal for any with a 3PL. I also decided that behind the seat was the best location. Here it does not impede the operator, tractor or implement operation (except the seat cannot be fully reclined, and I never do that anyway) is safe, is in the most convenient position, and the lid fully opens and stays open. Fitting implements and adjusting the 3PL is when you need a handy toolbox for spanners etc at the rear of the tractor.

I also decide the small red toolbox that suits the TEA20 and other MF tractors was the ideal size. I have a TEA20 so I know these toolboxes well. I mounted the toolbox to a steel bar bracket bent to shape and bolted to the chassis under the seat using existing holes, and also the side of the toolbox is bolted or riveted to the lights bracket on the ROPS, by drilling one small hole through the toolbox and the BX's bracket..
I have some photos and will try to work out how to attach them. The bar bracket was made from a length of 50mm x 4mm flat-bar, with a couple of angles bent into it. (25x 4-6mm would also be suitable)

 out of  found this valuable. Do you find this valuable?