Not sure where you are in PA, but there are no PA distributors listed. I will go with your closest state who has them: NJ! they are all authorized distributors for Settecento brand tile:
Start here- Wayne Tile: 973-694-5480. They have been around since 1953 and one of the go to places in all of NJ and many NYC folks. Depending how much you need, ask for a better price. They can order it via the phone. Pick-up might be worth a nice drive for you as shipping may be cost prohibitive.
Fuda Tile: 908-308-0110 (freehold, NJ)
Italian Tile Imports: 201-796-0722 (Elmwood Park, NJ)
Megan Tile: 973-673-6987 (East Orange, NJ)
Avalon Carpet & Tile: 856-834-5300 (Cherry Hill, NJ)
Tile Wholesalers of Newark: 973-589-2080 (Newark, NJ)
There is one online seller, who charges just over $5 a foot, plus shipping, but their reputation is not great. Folks claim it is one man show NAND nothing is in stock, and others think he is selling factory seconds. Who knows....I never used them. You can do your own homework on them: Value Floors Direct.
By the way...how old is the slab? If it's older and settled, and no cracks, the chances of it cracking are slim. A slab is cold in the winter no matter what, unless you heat it. A layer of Ditra has a minimal minimal in warming the tile, so little you won't feel it. Additionally, unless there are major pits, cracks or a huge slope difference, your mud is what you use to level. Adding a self level over a fairly level floor is a wast of time and money. It's a floor....not a lifetime commitment!
Good luck and have fun and measure twice!