You can get large bags of clean, high quality diatomaceous earth at most swimming pool supply stores. DE is used in many pool filters. I have a pool and use the same DE by spreading it around my hives. I still see a few SHB, but not many.
As far as SHB larvae crawling, Dr. Jamie Ellis (Univ. of GA) said that he once left a container of SHB larvae open in the laboratory one evening. This next morning they had crawled down two flights of stairs and were headed down the hall toward the door.
I've found it easier to keep bees than keep relationships. At least when I'm stung by bees I know why.