I purchased two Dance Dance Mario Mix pads (same thing as the hottest party pads) from nintendo.com about 1 month ago.
They are great. Price was resonable too ($19.99).
Web site: Go to nintendo store, in gamecube accessories area.
It's called the Action Pad.
I would definately get these. They work flawlessly with Hottest Party (yes I've used it). Even works with the calorie calculator.
FYI: The "Official Konami Pads" are the same as the nintendo Action Pad (issued with DDR Mario Mix). After a little research I've learned that the Nintendo version of the Konami Pad was manufactured by Nintendo. Basically, it's identical to the DDR Mario Mix pad.
Hope this helps.