When I referred to part number, it was to the plug - the thing that goes into the wheel to feed it power - not to the power supply unit itself that I referred. I'm sorry, I should have been clearer.
I was referring to a part number for a parts catalog for a large electronics parts manufacturer, for instance, so I could look the plug up in their catalog and get the dimensions and tolerances from there (as I live in Norway, if this plug happens to use some sort of inch-based system I am not optimistic regarding getting an exact match locally) so I can get hold of something that matches as closely as possible. As you can see in this wikipedia article: http://en.wikipedia.org/wiki/Coaxial_DC_Power_Connectors there are more than 40 different combinations of dimensions when it comes to coaxial power connectors like the one used by the Logitech MOMO Racing. I don't have the equipment neccessary to measure these myself, I'm afraid. I could probably get a connector at a local electronics shop or mooch one off the university, if I only knew the dimensions in question.
If someone could be so kind as to tell me the polarity and the dimensions of the plug (a part number or standards spec would be awesome) so I can build a replacement, I would be very thankful.