The only standard dumbell exercise I know of that hits the lats is the one arm row. Chin ups are the best and nearest equivalent to the lat pull down. I recall seeing in a book one time someone hanging from a chinning bar by their knees and doing inverted dumbell lateral raises and pull ups, but I never tried it. You might be able to do the same thing just standing on a platform and bending forward (like to touch your toes), although I don't think you could do too much weight before balance became a problem and it might be hard on your lower back.