I once saw a one-handed man in a second-hand store.
I said to him: "I don't think they have what you're looking for, sir."
The joke plays on the fact that a one-handed man might have difficulty finding something in a second-hand store because he is missing a hand. The humor comes from the absurdity of the situation and the expectation that a second-hand store has a wide variety of goods, but not specifically for people with disabilities.