Basically just wear your Max Damage killing machine equipment with as little MF as possible and then head out to any lvl85 area such as The Pits and start clearing...
As zemaj said, if you are playing single player then use the Players X setting, try and get it up to a high number without sacrificing your killing speed.
Battlenet.... well, just join a full game and go for it.
As it's been said, I wouldn't hope for a particular base.... It's taken me ages to find certain things but I've had quite a lot of luck with these sorts of items in the Pit.