When I was sourcing new spokes for my XS650 project, I wanted stainless and Buchanans brand spokes seemed the way to go. They make them, each one has a little B cast into the hub-end of the spoke.
Anyhow, I ended up ordering mine through East Coast Wheels. They were cheaper than Buchanan's direct, and charged less shipping. A little tough to get a hold of, but got my spokes and they worked like a charm.
Mine were non-stock custom spokes. Paid $80 a set for stainless nipples and spokes.
In comparison, Mikesxs sells standard spoke sets for $30-$40 I think. Just as a comparison. In my opinion, spokes are a lifetime investment, so the extra $40 per set seemed worthwhile.