I have had amazing success (found unknown cousins who went to Venezuela) using the Shoah Foundation index on JewishGen. But I was looking for an unusual surname (SPIELBERGER). Your surnames, WEISZ and KLEIN, will be much more difficult.
The rules for name with this database appear to be that women are shown by their married names. But if they mentioned relatives in their interview, you might find them with the relative's name. The first search on JewishGen in the Holocaust Database / USC Shoah Foundation-Survivor Interviews gives you a list of names. If you click on the View Full Record link, you will see a list of names mentioned in the interview and the relationship to the survivor. I think the JewishGen index only includes the person who was interviewed but the search includes all the names in the interview. To see the relatives, you need to drill down into the interview. But I am not certain of that - experiment with it and see what you find.
Peggy Mosinger Freedman
Atlanta, GA USA