You'll need to source from from the body of a 140/164 from 73 on, or a 240 up to 1985. In YM1986, they changed the design of that panel.
To advise you of a suitable body shop, you'll need to mention your locale. (Not everybody on Oz Volvo is in Melbourne....)
Caution is needed when cutting out that panel on the project car. It's advisable to cut more than you need from the donor car, then trim back what you don't need from the offcut. I've cut that section from a donor shell and it's not a small job.
