Bloomberg, Capital IQ and FactSet report current and recent supply chain relationships (customers, suppliers, and strategic partners).

Bloomberg - To display the suppliers and customers of a company, enter the company ticker followed by SPLC <GO> to access the Supply Chain Analysis function. For example, enter {AAPL US Equity SPLC <GO>}.

Capital IQ - search for a company, then select Business Relationships from the menu at left.

FactSet - go to the Company/Security tab and enter company name or ticker. Then go to the Supply Chain report or the Geographic Revenue report.