What's the deal with DOT physicals (see details)?

I need a DOT physical for a traveling job I’m doing starting August 14. They just let us know this a week ago, and they want the results by August 1, which is laughably ridiculous. The problem is that I’m on vacation in Maine for another week, and since I’m not from here, no doctor will do one for me. Every office I called said you need to be an existing patient. Well, obviously I’m not. I called my doctor in Pittsburgh and the earliest they could see me was September. My brother, who did this job a couple years back, said that there are places that will have signs along the road saying “DOT physicals – $50” and they’re just (usually) walk-in places that do your physical right then. So I’m banking on that, but I can’t for the life of me find a listing on the internet of where to get one, so what am I supposed to do when I get home, drive around aimlessly until I happen upon a sign? HELP! This is so frustrating!