If push came to shove, I'd substitute lettuce with finely grated cabbage. The only time I buy courgettes is when we're having roasted Mediterranean veg and DH isn't very keen on the texture anyway, but if broccoli were to disappear from supermarket shelves I'd go into a decline! as we eat it at least 4 times a week.
Betty Bromage wing walking at the age of 97


and I use them a lot in cooking for stirfrys. No yellow peppers either. I think you lot down south are taking them all before they get to us 
?????