I've seen a schematic for the BD-2 waza edition but never for the SD-1w. IIRC there was a freestompboxes.com thread but it fizzled out before a trace was completed.
My understanding is that one of the main differences is that it uses discrete components instead of an opamp, but no doubt they tweaked the usual components as well. Unfortunately, since the thing is built using surface mount components it's a pain in the butt to trace or work on so most people don't want to bother.
I wish you good luck in your search. If you do find one let us know. I'd be curious to see what the tweaks are.