Sorry...I didn't see your comment until just now. Hope its still relevant. The balcony was custom, sized for the opening and depth that I wanted. It also has a slight radius. Yes there are commercial products out there for small balconies that are somewhat pre-fab. In multi-family housing, they are quite popular and mass produced. One company I worked for called them 'decklets'. I always liked that designation. A simple Google search for 'prefab balconies' came up with many options. One is:
http://innotechmfg.com/balconies-window-railings

Came across your response to this member's question just now. What a great response. Thank you. I'm in the process of finding a juliette balcony to add interest to a big but poorly functioning window that we want to replace with a french door. Sounds like I should contact one of your colleagues before we proceed too far.