There are plenty of 4-way joysticks (easily demonstrable as such) that aren't Nintendo. So I wouldn't say it has to be Nintendo. And I don't understand why TG insist(ed) that it had to be stock. If a bat-top or something is more comfortable to a player, why not, as long as it's a 4-way?
I had to take a generic red balltop 4-way out of my cab actually when I bought it. And I have to say, in some ways that stick is more comfortable on my wrist during long sessions. I've been tempted to throw it in there for the tourneys.
The ol' Nintendo "loose tooth" is still my favorite though for DK.