IPA: /ˈstɒkɪst/
KK: /ˈstɑkɪst/
A person or business that sells goods, usually in large quantities, to other businesses or retailers.
The stockist provided the local shops with the latest fashion items.
Stockist → It is formed from "stock" (from Old English *stoc*, meaning a supply or store) and "-ist" (meaning a person who). A stockist is a person who maintains a supply or store of goods.
Think of someone who keeps a 'supply' ('stock') of items — the '-ist' indicates that this person specializes in maintaining that supply.