The toolbox is a Better Built 77213014 Deep Shotgun Tool Box. It has shotgun latches that don't interfere with the tonneau cover! Unfortunately, the SLE line from Better Built is being discontinued, but we hope they will change their mind. It's the only crossover/saddle style box we've found that plays nice with a tonneau cover! We found ours on eBay here: Item no longer available. If that listing is no longer available, search by part number on google.
Out tonneau cover used to be the Access Toolbox Edition Soft, Roll-Up. However, after a few trips with sharp turns, we realized that our pin box was hitting the rails. After about a year of this, the rails were trashed and we researched a different option with no rails.
We now have the Extang Solid Fold 2.0 Toolbox Tonneau Cover (84488). It fits perfectly with the toolbox and is much more secure than the soft cover was, with no rails. The drawback, however, is that it needs to be removed to tow the fifth wheel. So, we move it into our garage when we travel. That part is a bit of a pain, but it's not very heavy, and worth it when moving every 10 days to 2 weeks. If we moved more frequently, it might not be a good solution.