True, the Venice Casino could do it, as could banks. You could try the exchange booths at the airport, but I don't know if they would do it w/o undertaking another transaction. Another option: if you have an American Express card, then perhaps an AMEX office. You will not be able to use the note at restaurants, bars, etc.....

How are you planning on getting to your hotel from the airport: if you plan to take a water taxi (c. 100EU) - the Consorzio Motoscafi booth at the airport might accept it for payment and then give you change. However, you would need to go to the booth, do not assume that the water taxi driver would have that kind of cash on hand.