No need for a button. Like Crabby said, just put the gear shift in 3 instead of OD. And yes, of course, you will pay the price in fuel, as overdrive is merely a higher gear that lets the engine turn slower and use less fuel at speed.
The other option is to engage the tow/haul mode. This reprograms the transmission shift points and firmness. This may also decrease the mileage, but will somewhat improve performance. I hear that a side effect of this is that is also prevents (or significantly delays) shifting into OD, although I might be mistaken on that one.
-- SS