This is one of the early Intel powered Mac minis, these used the 110W power supply rather than the 85W power supply that came with the PowerPC based Mac minis. I don't see any of these power supply on iFixit but a quick search found two options through Powerbook Medic and Other World Computing...
Powerbook Medic - [http://www.powerbookmedic.com/Mac-Mini-Power-Supply-Adapter-110W---A1188-p-20528.html|$40 110W power adapter]
Other World Computing - [http://eshop.macsales.com/item/Apple/MA407LLA/|$46 110W power adapter]
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For what it's worth the Apple service part number is 661-6386.
This is one of the early Intel powered Mac minis, these used the 110W power supply rather than the 85W power supply that came with the PowerPC based Mac minis. I don't see any of these power supply on iFixit but a quick search found two options through Powerbook Medic and Other World Computing...
Powerbook Medic - [http://www.powerbookmedic.com/Mac-Mini-Power-Supply-Adapter-110W---A1188-p-20528.html|$40 110W power adapter]
Other World Computing - [http://eshop.macsales.com/item/Apple/MA407LLA/|$46 110W power adapter]
Hope that helps!