Quickest place would be in the trade forums. It's valued at Ko which is in turn valued at 10 Pgems. It doesn't take many NM Baal runs to get 10 pgems worth of items. People will frequently buy semi-useful junk for 1 pgem a pop. That's a bit optimistic of a value though. It's not incredibly rare, but people tend to hold on to them when they find them so it may take a bit more coaxing to get them to part with their AoKLs, but I would start with that price and see if you can get it that cheap.
If you want to do runs for it, Meph, Diablo, and Baal give the best odds of it dropping on their first kill superdrops. Otherwise NM Mephisto is your best bet. The odds of getting it from regular and superuniques skyrocket so I would stick to the boss runs if you're hoping to find it on your own.
It is an extremely useful wand. I only had a partial investment in skellies with my poison/skellimancer so they were dying pretty often and not doing a whole lot of damage. When I hit the level req and started prebuffing skellies with it they frequently started taking out enemies before I had a chance to poison them.