Just start shooting left handed. . . that's what I did and now I can shoot with either eye.
I was left eye dominate but right handed. Dad forced me for years growing up to shoot right handed with scopes and without. Then in Hunter's Safety at age 13, I found out the issue. So I started shooting rifles left handed. Pretty soon I was confortable shooting long guns both left and right handed, I shoot pistols left and right handed also. I found shooting left handed was smoother... 20 years later I'm confortable enough that I switch hands depending on the shot. If a duck is flying by from left to right I shoot left handed, if a duck is flying from right to left I shoot right handed. It gives me a further swing. Guys duckhunting with me like this also, depending if the guys right or left handed I just sit on the other side so I don't mess up his swings. Its the same with pistols, weak side barracade I shift the pistol to my other hand. I keeps me behind (cover/concealment) easier. So if and when I end up with one of my eyes not working so good, it shouldnt be a big difference. It just takes practice. And I don't shoot special left handed guns either. It's not like they issue the lefties in the Service left handed M16's.
And to answer your question I have never seen a scope mount to shift it to your left eye. I believe the reason is the further away from the bore a scope is, the more it screws with the points of impact.-WW