I got mine from
www.etrailers.com
They had three different models that fit the Tundra.
I got the Hidden Hitch brand.
They also provide the installation instructions online (so you can see what you are getting into before you buy).
They have some FAQ sections to help you with other towing questions like "how much of a drop do I need".
And their prices seemed fairly reasonable. The shipment arrived within a week of ordering.
I have the receiver, but have not installed it yet (due to 24" inches of snow falling!!!).