Since art. 250.68(C)(1) states the 5' rule, I'm SOL. I will need to add a dead front at the panel so I can install a 3-prong receptacle. I have no access to run a new wire from the panel. Gotta love remodels, people want everything with the least amount of damage.
You have no access? There is no rule that says this lone ground has to be without splice or can't take a convoluted path. You could run it from the panel, or the outside ground electrode, up the outside wall, along the wall, into the wall or eave, and over to where you need it to go. You could also find some other existing EGC (if of sufficient size) and extend it. About the toughest place would be an internal wall in a middle floor (with above and below floors finished). If you did this with a single #10, you'd have a common point to branch from for other grounding tails for other outlets. Sometimes you can get lucky and find an old phone cable or something else you can use to pull a green ground through a wall without having to tear it up or try and bore through it. Managed to do that at my last house from basement to attic so it didn't have to run up the siding trim.