What do you consider a “ninja” and how much are you willing to customize to get that classic dude in black jammies look?
McFarlane has a lot of options
Ghost Maker from the DC line has kind of a modern tactical ninja look but is in off white clothes
Edit: after seeing them in a search to see if Ghost Maker was even still available for a reasonable price Talon and Abyss have potential too
In the MK 11 and MK Klassics lines you have the “Ninjas” (Scorpion, Sub-Zero, Reptile, Noob) and Raiden (who wears white but his costume is not fundamentally different from the ninjas) Lui Kang could also work if you want a topless ninja. And if price isn’t a concern Storm of course had a lot of these fellas available as well. They’ll just need painting to color the pretty candy color to make them clad in black.