Scali is unique to Boston and in fact was created by the Scali family. Boy do we miss the trips to 24 hour Bova's in the North End at anytime of the day to buy Scali bread and a whole bunch of pastry. Such great memories.
We have made it here homemade but it is a two day process because you need an overnight starter.
The closest thing I have found is a "French Bread" at Walmart of all places that is covered in sesame seeds like Scali. It's not the same but there aren't any real substitues.
Here's a trip down memory lane for you Bostonians:
Bova's Bakery - Boston's North End Bova's Bakery