Kueh Paiti... (or something) can be bought from the Chilli Padi stall at the basement of Tangs. I think.
Or I think Takashimaya basement also has it.
And you may also want to check out the Peranakan stores along East Coast Road, opposite Katong Village (the food place).
Food-on-the-go... I can only think of sandwiches.

They're easy to eat, minimal mess... and you can put some special filling instead of the usual ham or tuna or cheese or egg... Like umm, ah, YAKISOBA BREAD!
