Hello,
I rarely go to the Coop, but when I do, I always buy the Caesar dressing from Mövenpick. This is a real gap in the Migros range and might be worth checking out - and maybe there's still some space next to the 6 French dressings already on the shelves.
Lettuce (roman lettuce) is available at Migros both fresh and as a convenience item. Croutons too. That would provide almost everything except the sauce.
Thank you for your consideration of the suggestion.
Regards,
Stefan