Big women or small. They are everywhere. They are in the mall, the bar, the park, the local store. All you have to do is approach them. Don't be nervous. Start by saying hi and then continue from there. What are you afraid of? They won't bite you. You'd know exactly what to say once you get the typical "hi" from them. Comment on their clothes, shoes anything. Be yourself and everything will run smoothly. Just try to stay away from crazy "pick-up lines" which are a big turn off.
I am not sure if this will help you enough. But if a guy was to come to me and say hi. I'd definitely help continue the convo. And then again, this is just my perspective.
Grocery stores. Bars. Fast food joints. Sounds derogatory, but true. These ladies like to eat, obviously. And beer isn't exactly a slimming beverage. Check those places out. Start at the grocery stores. Tons of ladies there (no pun intended). Good luck.