Better Built 79010946 low-profile saddle tool box, $150.
This is a high-quality all aluminum tool box for a small pickup. I used it on my first-gen Toyota Tacoma, I'm only selling it because my truck was totaled. :-(
It'll probably fit on any small pickup like a Toyota Tacoma, Ford Ranger, Nissan Frontier, Mazda, S-10, etc. It comes with no-drill mounting hardware. Bring your truck and we'll try it out!
It's no longer in production, but similar models from Better Built are selling for $450 to $500. Here's an old amazon listing with pics, etc:
https://www.amazon.com/Better-Built-B01C5IN150/dp/B01C5IN150
The struts are still strong, and still lift the lid just fine. It unlocks and opens from either side. The low-profile top makes it look pretty sick installed on a truck.
The bottom measures 39.5" long, the "step" is 52.25" and the top is 62.5"