Oh my... I think your best bet is to make the horns out of papier maché.
Last year, the Party Bazaar on West 2nd Ave. had some soft-foam gold lamé horns (supposed to look like Tim Curry's horns from Legend I think; kinda goofy but you could paint them with fabric paint to make them seem more realistic) which if they still sell them, you could stick a coat hanger wire inside and bend them. They were near the wigs section - maybe just ask the staff if they have any kind of headgear with horns. Even some sort of Viking thing would do if they can be bent somehow.
Otherwise, on this short notice, I think you're buggered, mate.
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