I would suggest, in order of nearness to DE and heading toward Dutch (where they will likely take you for the in-water part): Scubadelphia, NESS, Indian Valley, Atlantis Aquatics, LVDC. All have instructors who can teach drysuit.
I also have a few independent instructors names for you if you want to go that route. They will typically offer to combine drysuit with another class for what works out to be a reduced fee over taking the classes individually.