So after some searching I found a part number for a XC60, T8 PHEV, charcoal color, right side tunnel panel that had a mesh storage pocket. I bought it thinking that it might be a direct fit for my S60. Turns out, this is not the case and the part will not work directly. But, it is possible to remove the mesh pocket from the XC60 part and fit to a S60 or whatever.
As it comes from Volvo, the mesh pocket is plastic welded to the panel in multiple places through holes in the carpet and plastic panel. These welds can be chiseled off and the pocket frame will pull away from the panel. There will be some portion of the attachment left on the frame, this needs to be filed off so that the frame can sit flush on the side panel (I used a bench grinder). Then, the frame needs to be attached to the original panel. I used M5 x 16MM button head torx screws with a black oxide finish sourced from Bel-Metric with the screws passing through the original plastic-welded locations, then attached with a flanged nut on the back side. The 16mm length was a little short at the ends of the frame where it is slightly thicker, if I were to do it again I would use 20mm length screws. They are a little long elsewhere, and I ground down the excess and a little of the flange nut on all the attachments anyway to make them as flush as possible on the back side, so a longer screw would make an easier install and just be a little more metal to grind away.
For anyone trying this, I think it is not needed to attach the frame in all the original plastic weld locations. In my opinion, my install looks a little busy with all the screws and probably half as many could work just as well.
The part number of the panel I bought is 3149612, it was about $80 IIRC.
Original panel from my S60 T8 and the XC60 T8. The S60 has a notch at the top that is not present on the XC60, but also the fixing posts on the back side are totally different. Here you can see the locations of the plastic weld points. I had already drilled through the centers of the back side posts before I chiseled off the welds so I was committed to using all the OE attachment point for this mod.
Attached, back side view:
Installed. Using all the OE attaching points is a little busy but it looks okay. If I were to do it again, I would use fewer attachments and space them out farther apart.
XC60 part:
Hardware:
Overall, it worked out fine and follows the OE shape. Also, it is great to have a place to store my phone.