What I do is plan leftover meat at dinner time. For instance, if I'm cooking chicken or pork or beef or even burgers for dinner, I cook extra and use the leftovers in my salad for work (sometimes an extra dinner or 2, also). In a real pinch, I LOVE Goldseal Smoked Tuna Slices which come in a zip open type can inside a box, at Safeway. I think there are 3 flavours.

I find that a "harder", chewier meat as mentioned above is more filling for me than canned salmon or tuna. And my salads generally have 2 kinds of lettuce (leaf, romaine, escarole, curly endive, spinach), maybe cucumber, mushrooms, a bit of green pepper, and usually 1 Tbsp real bacon bits, 1 Tbsp feta cheese and about 2 Tbsps commercial LC dressing (ranch is quite low carb. There is usually about 3 cups of greens, btw. I have done this since the beginning, with no problem staying under the 20 carbs.

Hope this helps!

BTW, did you know you can get any of Subway's sandwich combos made into a salad? Unfortunately, their dressings are usually low fat, but you could bring your own! Also lots of grocery stores sell chicken breasts and wings - another emergency source for lunch (altho not the best cos they do use seasonings/bbq sauce that might have sugar). Bun-less double meat burgers are another option.