Double X Negative 5222 is in fact the only B&W motion picture negative film in the Kodak Motion Picture Catalog. Must be ordered directly from the Kodak Motion Picture folks, in 400ft rolls.
if you are in the states or Canada the details are
EASTMAN DOUBLE-X Negative Film 5222 / DXN718 / 35 mm x 400 ft roll / On Core / BH-1866
1737279 $177.60 ( a thousand feet are $444 if you can deal with that big a roll)
to order you have to call 1-800-621-FILM (3456)