Places to sleep in car overnight (short time, 7 hours? passing through)

Looking for suggestions on a place the sleep overnight in our camper van en route to northern Maine. Our itinerary would have us just around the Maine border - we'd love to check out Kennebunkport in the morning on the way north so anywhere near there or roughly an hour ish south?
- Had considered the Northbound travel plaza but have seen other users state that there are signs there that only allow 4 hour parking. Wed be parked probably about 6 or 7 to catch some shut eye.

-Usually we will stay at at Loves travel spot but there don't appear to be any near here, and the closest wal mart is not open 24 hours so I'm afraid that's not an option.