This mob spawns at the second floor of the SSW building at 193, 616, 129 and also at 19, 738, 148, on the first level of the ramp overlooking the room where Halgin is.
I also found her at 19, 738, 148, on the first level of the ramp overlooking the room where Halgin is. I've seen 'an inventor' as the PH a couple times.
After a week of fruitlessly clearing the center rings and the bridge pathers I finally found the Shop Sweeper ph on the second floor of the SSW building at 193, 616, 129. Shop Sweeper does path but I had just entered the key phrase to spawn Lady of Pain as she started to path. Killing Lady of Pain gives you the update.