According to
Minga (link in german) there are now oktoberfest armbands. There's a picture on the site, which I would post here but won't because of copyright. Basically they aren't for any charity, but will get you free entry to Volkgarten, 2 Rooms, Apartment 11 and Barcode throughout the Oktoberfest. They cost 5€ and can be bought under
Sportsband.de, which obviously isn't bad if you go to one of these clubs regularly...