I am making an assumption that the side boxes have a single door w/ a pretty simple lock setup. You might be able to remove one and look for a generic that will use a SnapOn style key or even look to see if SnapOn has a similar lock for their own side boxes. BTW once you web search for these type locks you will see that many of them come w/ replaceable cams. They are generally made from sheet metal and remove w/ one screw. So, if you find a cylinder that fits (maybe a SnapOn) but the cam isn't quite right, it can be replaced or removed modified and reinstalled.