Locating poison charms?

[SpaceFalcon]

Anyone know where I can find them easy?

I got a GC 50 poison dmg charm in norm d run, and a 50 poison dmg sc from a box in cow maps.

Is is just sheer luck and randomness or does this actually drop from certain monsters?

[Delreich]

Lots of luck, and some small amount of knowledge.

Have a look here to see what ilvl is required for the various affixes:
http://forums.diabloii.net/showthread.php?t=403178
... and then go find charms with high enough ilvl and hope for the right ones.

For items droped from monsters, ilvl is equal to mlvl.
For nightmare and hell difficulties, mlvl is equal to area_lvl, so use this:
http://strategy.diabloii.net/news.php?id=551#Area%20Levels
... to find suitable targets.