Try googling mens (or womens) elephant bell bottom pants. I had some of those in the 70's. :afro: You may have to buy them used, and or pay alot for them. Or try mens (or womens) loon (short for balloon) pants, maybe?
I know it's not what you're looking for but I make rave pants...sorta close, but I don't think they even make bell bottoms anymore your best bet would be to make them yourself