I searched quite a bit.
I know KOBALT makes one for the stepside narrow beds, but couldn't find it at Lowe's website.
I've seen a Black Husky one on another guy's truck, but I don't know where he found it.
Here is what I did find though.
Dee Zee
Part# DZ8150B
Red Label; Single Lid Crossover Tool Box; Gloss Black; Volume 5.8 cu. ft.; L 50 in. x W 20 in. x H 12.2 in.;
Sell Price:
$344.99
and
Dee Zee
Part# DZ8150
Red Label; Single Lid Crossover Tool Box; Brite Tread Aluminum; Volume 5.8 cu. ft.; L 50 in. x W 20 in. x H 12.2 in.;
Sell Price:
$320.99
Website that carries both:
http://www.toolboxes4less.com/