Chris - you may want to try one of the car advertising rags... like Autotrader or Cargurus. I'm sure there's others. Worth a shot. I input BMW/2003-2006/sedan and then typed ZHP in the keyword field and got these. Maybe there's a relevant comp in there:

https://www.autotrader.com/cars-for-...xtension=false

https://www.cargurus.com/Cars/invent...Modified=true#