Eastman 5222 (Double-X) can be purchased directly from Kodak in 400 and 1000 ft lengths. There is also the possibility of buying "short ends" which would be a cheaper alternative. There are several sites that sell short ends.
BTw, Kodak cine films are marketed under the name Eastman rather than Kodak. The films are numbered either 5nnn (36 mm) or 7nnn (16 mm).