AFAIK at
BetMoose you can create bets on special events that are not listed on other betting sites, I haven't used betmoose so kindly do your research before sending any money to the site. And I think there might be 1-2 more sites like it which allow you to create bets on events which are not covered elsewhere.
You can also start a thread here, maybe some BigBrother fans will take some bets, but for that you'd have to arrange for an escrow.