I see a lot of Megadrives on sale at eBay as console only without PSU. Does the PSU have a standard shaped/sized socket? i.e. Can I buy a generic PSU to use this console, or will I need an official PSU?
Wikipedia gives the connector types for two of these models:
So, going back to the chart:
As mentioned on the GameTrog page, be sure to match the voltage if you decide to go with a 3rd party PSU and be sure it can deliver at least the amount of current specified for your model. An incorrect power supply can damage your system and potentially yourself. Overall, I recommend finding an official PSU.
I don't recommend to choose yourself a power adapter, you can go it right or not. Last time I buy a power adapter for my Sega consoles I went to : http://en.retrogamesupply.com/collections/sega
They clearly know their stuff. They also have other power supply for a lot of old console.