Does anyone know of anywhere where these might be found?

Richters seeds is a good source for herbal stuff. I doubt if Tropical forum knows much about herbal sources. I doubt if any one here at the moment knows much about herbal anything. They all left a long time ago.

Richters
Horizon Herbs

You can also try asking in the "Herbs" Forum. That forum is plant-centric - generally about growing and using both culinary and medicinal herbs.

FataMorgana

http://www.lazyssfarm.com/Plants/Shrubs/S-Z Shrubs/shrubs_trees_S.htm Has a cultivar of Salix Alba, so not the wild type, but its what you get for free, just take seeds off of it eventually and plant them if you want a whole plant.

As for Quinine thanks to Evolution it isn't the most effective mallarial treatment any more, but it is still very effective at reducing leg cramps.

""We believe unapproved quinine products represent a serious health risk because of the widespread use of this product for treating leg cramps," Steven Galson, MD, MPH, says in the FDA news release. Galson directs the FDA's Center for Drug Evaluation and Research.

"Quinine needs to be dosed carefully, and FDA-approved labeling reflects the fact that the risks associated with the use of this drug for treatment of leg cramps outweigh the benefits," Galson says."

Of course, using a 3X homeopathic quinine preparation (a 1:1000 dilution) would lower chances of toxicity, while raising the likelihood that you're just wasting your money with a product that's virtually all inactive filler.