There are a couple of places where we buy gear from:
Sherrills, Bisho's, Rope1, New Tribe and Wesspur but most "selling" of gear is not done here for concerns with liability of faulty or defective gear ..... and being associated with potential accidents and lawyers and all that jazz. Hope that helps.
Treebuzz.com has an area where Arborists buy and sell their gear person to person on private messages and such.
Are you a Recreational Climber or Arborist worker?