I came by a nice camera in very good shape, except for the missing ground glass and plate magazine. It is a Contessa Nettel Deckrullo NR. 120 (10cmx15cm size negative and with a 18cm/f4.5 Tessar). I believe the size is very close to 4x6 inches. Does that mean that I need to get a 5x7 ground glass and cut it down to 4x6? Any good sources for ground glass outside of Ebay?