You might also mention where you're located, since seller location and/or shipping cost can matter.
In the US, there are lots of plugs at electronics supplier 'sites like Digikey, where they have a drill-down selector where you pick # of pins, size of pins, pin spacing, voltage and current rating, etc then look at the shape of the housing, plug, or socket they're in.
You might also tell us the make and model of coffee cup, even better to link to it if you can find it online.