An offset flange will work only if you are able to make a straight cut on the 3" pipe connected to the current flange 3" below the top of the floor and still have 1-1/2" of pipe left to glue the new flange to. I bet this is not a likely possibility.
An offset flange will give you 2" of offset in any direction. If you only need an inch of offset, the center of the flange will have to be slightly left or right of the current center -- think cam. Installing an offset flange from above is one of the most difficult things a plumber has to do, and most times, it simply just can't be done. If you have clear access from below, it is not so bad.
Bruce