Sorry, Frank, I didn't see this post earlier on.
Enkei is an aftermarket wheels company, and here's their North American webpage
http://www.enkei.com/enkei.html
Maybe Enkei has worked up a deal with Toyota to sell aftermarket wheels through the official Toyota dealerships, but I think various other aftermarket wheels companies do the same thing with various manufacturers.
In terms of fitment, maybe it'd be best to compare the measurements on those Enkei wheels to a set of OEM wheels on a Tundra. Unless there're other owners here who could chime in for that matter. Good luck and let us know how it goes