If they are the bolle goggles you could try removing 1-2mm (depending) from each side of the lens and then fit the lens into the rubber frame with a bit of glue.
If its the dust goggles, you could cut away the lens from the frame, shrink the frame in acetone, then shave down the sides of the lens and glue back into frame.
I've tried the first method, and it works ok but isn't 1:1 accurate. Be careful not to use too much glue or you will fog up the lenses.