[Skyhammer]

It is a paper element and if you are careful, you could clean them but they will be fragile.
As far as after market, they should be available, although I haven't looked for any for the Tundra.
On the Titan for example, it used the same filters as all other Nissan models, so they were avaialbe at NAPA for $10 less or so than what NIssan sold them for.
There were also permenant, lifetime, washable filters available in plain or in an activated charcoal version. These were about the same price as what the dealer wants for one of theirs.
I would expect that these filters would be available for the Tundra as I expect that these filters are used in Toyota's other models.