I had a similar problem with a tang mounted peep on a Remington Model 141 pump gun. Cut a couple of strips out of an empty soda can and put two of them under the right side of the sight base. For me, that was enough.
You don't say how far you're off to the right, so you'll need to do some math. Basically, you want to move the center of the hole in the peep (not the base) to the left in the same proportion to the front sight as the bullet strike is to the right at the range you are shooting. So, if your sight radius were 36 inches (1 yard) and you were 10 inches to the right at 100 yards, you'd want to move the center of the peep 0.1 inches to the left. You'll have to experiment with the shims to see how much each thickness moves the sight.
Get it within 2 inches or so to either side and call it good. You're shooting at minute of deer, so anything that puts a bullet into a basketball sized ring will hit the kill zone.
