Hey Rush96!
Mustard Greens is an American term, and to be honest, I'm not 100% sure what they are!
Endive is definitely an Australian green - I usually get mine from Woolies in the fruit and veg section. However, at the moment, according to "my people" down here, it's not readily available at the moment - out of season I think...
Escarole is another American term, and again, not 100% sure what it is!
If you can't find Endive, use extra Bok Choy, Parsley and Watercress in lieu of endive. I had to do that the last batch I made (I make a 90litre tub at a time, handful in each freezer bag, pop them in the freezer. Just remember, the freezing process destroys Thiamine (Vitamin B1), so add a pinch of Thiamine once a week, and you should be fine! (you can get Thiamine tablets from any Chemist or Health Food Store - crush with a mortar&pestle - or between two soup spoons - until finely 'powdered', and store in a cool, dark place.
Hope this helps, and I'm really sorry I didn't reply earlier (haven't been on here in a while!)
Best,
Carolyn