Healthy fats and protein can form the basis of your diet but you could include things like full fat yoghurt or high protein yoghurt or the Quark deserts, nuts, eggs, avocado, high protein nut bars like Nature Valley, KIND or shop own low carb less than 10g per bar.
Sorry I didn't welcome you to the forum. I hope your treatment is going well.
You should perhaps ask your oncologist if the weight loss is normal with the treatment you are having otherwise it may be worth keeping in your mind that you may have Type1 or LADA rather than Type 2 as the unintended weight loss can be that. What are your blood glucose levels like.