Does anyone know where I can pick up a set of footpegs that are farther back than stock. I just got a new pair of boots and it's harder to shift.

 

Generally that requires a modification to the mounting position of the pegs rather that new pegs. The new pegs would be made to fit your stock location. Many riders modify the pegs to be 1" back & 1" lower for better handling & easier lifting of the front end.
If you only reason for peg location alteration is to get your toe under the shifter, why don't you simply slip the shifter off the spline & move it up a notch or so?
Just as a side note, years ago when riding observed trials, many of us would move the shifter to a vertical position to escape rocks or other obstructions in a section. We would shift with our shin bone or back of the calf.