I have a couple pieces of leftover spalted sassafras. They're the offcuts from the edge of a slab. The spalting is in a few spots; otherwise the material is clean.
The sizes are approximately 2.5 X 86" and 2.25-3.5 X 49". It's 8/4 lumber in the rough. Of note, it appears that sassafras oil has mild toxicity; though I had no reactions while working with this lumber, you should do your own research.
The material is available for pickup at my workshop in the Santa Monica/West LA area.