Just about every airport has an FBO that has the computer to take any of the FAA writtens. However not all these schools will be able to do the flight training & ATP check ride. If you need to do the check ride too, you can get a package that includes the written & check ride & training. Probably the most reliable course is with ATP Academy - I didnt train there or work there, but several of my instructor friends have done their program. Dont forget, the written is good for 2 years before you must take the check ride. Good luck.