We found that the Chagall Windows are at the Hebrew University Hadassah Hospital in Jerusalem . The best way to get there by bus is to catch bus number 19 or 27 and take them to the last stop of the line, which is actually at the hospital. The windows are well worth seeing, not only artistically, but historically. The tour is quite good, although it's closed from 1 - 2 pm for hospital staff prayer. The shops there are also closed on Shabbat.
Admission is free.
These are very reasonably priced and I took the tour to Gaza which I very much enjoyed. We were taken to the Erez checkpoint then picked up the other side. We went for tea with a refugee family, visited a mosque and the Greek Orthodox church in Gaza, had lunch followed by coffee, hubble bubble pipes and a trip to the PLO flag shop, drove past some Israeli settlements, visited a non-government organisation and went to the beach before returning to Jerusalem. The tour was political but not uncomfortably so and allowed an insight into Palestinian life that would be difficult without a local guide. As a woman travelling alone , I found men consistently courteous and helpful, which allayed my fears about Middle Eastern hassle.