best machine for low back problem

[fatjack]

I'm new to this forum [and fitness] and am almost 60, 30lbs over weight, with lower back problems [sciatic] and am considering getting myself a machine for my birthday to motivate me to excercise at home. don't want to go to gyms and it's too hot to walk. internet research has led me to believe that an elliptical type machine would be best for a fat lazy slob with a lower back problem. any advise would be appreciated.