Yeh, horse-hair is hard to come by these days!
Some of you guys have cats. You could just start collecting cat fur and glue that to the walls. Let me know how that works out! Be sure to take some waterfall graphs before and after. I think coughed-up fur-balls might work just as well, if you're having trouble getting enough volume from the couch alone.
EDIT: apologies to offnote. It's Friday night, if you know what I mean. But the thread was really doomed as soon as Beavis & Butthead made their appearance.