I've seen Double Cab Tacomas with roof racks. How can I get one for mine?
Under normal circumstances, Toyota only sells the roof rack pre-installed from the factory. (Factory option code: DR, $220 msrp)
This is because the roof rack requires the truck to have a specially reinforced roof skin. The roof rack began appearing as an option on 2002 models, and quickly became unavailable as of early 2003, discontinued due to lack of demand, and difficulty on the assembly line.
Digging deeper, there is only one possible way to get a roof rack for a truck that did not come with one from the factory. It is available, piece-by-piece as replacement parts through the Toyota Parts Department. However, this is certainly not cost-effective. The dealer cost for all of the parts is $1157, with a msrp of well over $1500.
JAC Products manufactures the rack for Toyota, but since Toyota owns all of the rights to the rack, JAC Products is not at liberty to market or sell the rack. JAC Products also manufactures roof rack systems for Ford, GM, Nissan, and many other auto makers.
Here are the part numbers for the roof rack components, if perhaps they are needed for further inquiry:
8 metric M8 Nutserts (or Rivet Nuts) can be used to attach the rack. Nutserts are rivets with internal threads that can be mounted and accessed from the outside of the sheet metal. They allow fasteners to be mounted to the roof without having to remove the headliner. Nutserts require a special tool and they can be found at a fastener supply company.
There are a number of aftermarket roof racks available for the Tacoma Double Cab. Thule, Yakima, and several other specialty companies manufacture universal racks for nearly every vehicle. Many dealers offer a standard style dealer-installed rack. There have also been Tacoma owners who have transplanted racks from Nissan Frontiers and Ford Explorers quite successfully.