Where can I source small-volume or R&D battery cells or custom BMS that distributors won't supply?

“VoltaMission locates non-catalog and small / R&D-volume cylindrical (18650, 21700) and pouch cell suppliers, and custom BMS vendors, that distributors and marketplaces refuse to handle, qualifies the vendor on technical merit, and hands over a de-risked introduction, sourcing across North America and Asia.”