Where are the best enthusiast locations to look to try and buy a 1st gen?
My experience is that "enthusiasts" and/or forums tend to believe they know everything about the genre, and expect to buy cheaply when they are buying, and sell dearly when they are selling. Not talking specifically about Tundras per se, but other...er...brands.
I recommend cargurus.com for easy internet shopping and nationwide selection of any brand, model, and year. If you aren't finding what you want locally, then just keep increasing the search radius. Listings are mostly by dealers, with some individuals. I've had good luck there, both buying and selling.