I also have the same problem, right hand shooter with a left dominant eye. i have tried a few things like wearing an eye patch, and closing my left eye evan tried shooting off my left shoulder.
I find closing my left eye is the best remedy for shooting game, but for shooting clays i wear a clear pair of glasses with a small piece of sellotape fixed to the centre of the left lense to block the left eye from focusing on the target. The tape does not have to cover the lense totally, a piece about 1cm x 2cm does the trick just enought to cover your eye. It has to be a non clear sellotape.
