Are you looking for something that is exactly 1/2 width and fit to the truck bed? If not, there are drawers available for commercial vans that may work for you. In various lengths.
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1-Drawer Stack Storage Unit-12"W x 6"H x 50"D
1-Drawer Compact Stack Unit-12"W x 6"H x 50"Dwww.americanvan.com
Truck Vault makes some incredibly quality drawers. If I could justify the price of buying pre-built drawers, they would be with whom I'd be going. I'm fairly certain the offer the most customizable options amongst the competitors, and their customer service is top notch.
Why not go full length and put the kennel and fridge on top?