for a replacement for the london bridges i think p90x2 lever pull ups will work.

I substituted them for a similiar sort of excercise, laying down lat pull ups... or another good one would be cable rows working each arm independently

I am also curious of this lol.

Im also looking for an alternative for this.. Today I tried laying down lat pull ups using TRX bands..

i take the smith machine upside down, and do pull-ups, but 1 arm working at a time. So I basically hang on an angle as one arm is straight and the other arm is contracted. works pretty good using a close-grip.