I'm not sure what the chance is of getting holy water for sale; I was half done the game when that was added, and didn't visit the BF very frequently. IIRC, one person reported finding holy water 2 or 3 times in the first act BF, but that is not typical. Near the end of the game I quicksaved, then entered the BF repeatedly and quickloaded if the traders didn't have any holy water or good equipment to buy. It took an hour to get some, literally on my last attempt (after trying for awhile and finding some slightly better equipment, I set a deadline so I wouldn't waste too much time reloading).
