Search on YouTube for BENTO BOX, which is a posh Japanese lunch box
Some of the food & recipes contain rice and other unsuitable carbs & ingredients, but many of them are based on meat, eggs, fish, vegetables, and some fruit.
So if you select and adapt you should find some interesting ideas
Try these for a start; obviously miss out sugar & rice, and if you can't manage chop sticks (I never have) just take a small fork & spoon or a KFS set for camping
The full video on YT has recipes
Bento lunches are an introduction to Japanese food in general, which uses mostly plain, simply prepared ingredients
The home kitchen based meals are interesting, if you miss out the carbs - Search away!