Toolbox for a lawn mower

I have a long, narrow piece of property, and at the back of it I have a workshop. For various reasons, I can't be too sure my workshop is secure. I tend to keep only the bare minimum stuff there, and I tote the more expensive stuff back and forth when I go out to work on something.



Now I know the most sensible thing to do would be to buy an ATV to go back and forth. But I have a Sears riding mower, so that's what I use :)



I don't want to buy a trailer because to me that's a hassle. It double the length of my mower, and it makes backing up and storage a hassle.



So I'm looking for a toolbox I can attach to the mower. Anybody have any suggestions?