You could do ss+ which is 3 shakes and a 200cal meal eg chicken, fish, cottage cheese amoungst other things and some veg, ask your cdc for portion size of these things, ive read on here the losses for ss+ are much the same as ss.
Hi Gem - the SS+ plan sounds very similar to the W8 regular plan. Packs plus a small meal of low-fat protein and green veg/salad - the weight losses are very similar to SSing as far as I can see. If you can't get hold of your CDC I'm sure someone would be able to tell you the allowed foods/amounts (we are allowed 3oz/100g protein if that helps).
I'm sure if its a choice between adding a meal and falling off the wagon - adding a meal would help you stick to it.
Gemma I have an electronic version of the pink book which gives portion sizes for the SS+ option, if you want me to email it to you, pm me your email address.