Hard to tell from your pics, but is it pushed into a corner i.e. up against wall and/or fence? Yeah, that'll be a problem. But on the side(s) where you do have access, can you not just cut the sprayed foam back so it's inside the support framing? Then you could add at least
some panels like mine:
View attachment 625500
The access down here is poor (as is my photography), but you get the idea. The two silver panels are the ISO I described earlier. The pink one is a replacement for the ISO that was too busted up to reuse, and just what I had handy, because any insulation is better than none.