BOC Sciences provides a series of chemicals related to alternative photographic processes, including platinum, palladium, gelatin, and sensitizer, etc. Orders both in bulk and by individuals are welcome.
A review on 14 December 2020: They do still supply chemicals, but it’s not in their catalog.
You need to search for what you need, for example:
Company name: BOC Sciences
Address: Shirley, NY 11967, USA
Email: account (at) bocsci.com
Ship: Locally and internationally