I have 6 black power supplies with round connectors.
1. AC Adapter, Class 2 power supply, part number 70D0210, 30V, 830ma - $3
2. Hewlett-Packard power supply model C2175A, Output: 30V DC, 400mA, 12 VA - $10
3. Scientific Atlanta model DA30H12. Output: 12V DC, 2.5A -$5
4. LiteOn model PB-1360-3SA1. Output: 12V DC, 3Amp - $5
5. IBM Part # 02K6543. Output: 16V, 3.36 A. Round connector 5mm, polarity - inner plus, outer minus - $5
6. SIL Class 2 power supply, model UD-1203B. Output: 12V DC, 300 mA. Round connector, polarity - inner plus, outer minus - $3