I've just recently treated myself to a Nikon FM2, which was a better price due to a missing rewind crank arm. You can still rotate the circular part with your finger, but because the arm is missing, it's very slow.
That being said, does anyone know if this part is standard on any other nikons? I'd like to find a junker body and cannibalize it, but there are very few junker FM2s.
Most independent repair shops will have a box of these and should be willing to sell you a handle.
Are you also missing the small spring that goes under it to give it tension? It's not a coil spring just a piece of oddly shaped metal.
If nothing else, go to the bay, category "cameras" and "parts" It will give you a choice of sub-categories, film cameras is the one you want.