Chris King makes a "Devolution" headset that lets you do just this.

I have no idea how much it costs, or what the availability is like, but afaik, King headsets ain't cheap... Cost-wise, you end up better off just getting a correct-sized fork.

Also if you are trying to use a 1" fork with a _threaded_ steerer, you are probably just out of luck since the King headset is threadless.