Karen, I purchased two baskets of "Black Velvet" petunias from Menards this spring. The planter that was in more shade stayed true, but the one that was in more sun actually started to develop the yellow star, making it look very similar to "Phantom". Unfortunately, I never thought to save seeds from that one, and I pulled that planter last week.
I'll bet seeds will be available eventually. I was surprised to even find the plants at Menards--they're not usually known for their cutting-edge purchasing