You can install a 1" Pachmayr or Silvers Repro pad with a black phenolic spacer, or you can fit a longer pad such as the 1-1/2" Silvers Repro. Either way, it will look clunky on a 28ga. Cost about $100+/- depending on who does the work. I'm putting a 1" Pachmayer on a Beretta straight grip 28ga Onyx that is too short for me. I don't like it, but it's the only practical solution for that gun.
Randy McCune posts here as RMC, and his brother fits carved wood butt plates to older shotguns. He has posted pics here, and I have one of those guns. Very nicely executed. You might contact Randy.
You could always look for a new stock, but that could take years.
