I've seen tons of game-used items on eBay for different athletes. You got gloves, batting gloves, jerseys and bats. Those all fall within the norm of game-used items.
On cards, you see pieces of hats and things along that nature. Even game-used swatches of pants.
But, do you really want the whole item. Here's an eBay auction for Kevin Kouzmanoff game-used pants.
The whole thing.
Not sure if I have seen pants before. Before anyone asks, I am not buying them.