I briefly looked into how you make a food safe painted plate at home and the answer seems to be "easy if you have a kiln".
You might be able to find a paint your own pottery store near you. I went to one with some friends and it was a lot of fun and I got a colorful owl coin bank for like, $10 or something. Just have to make sure it's food safe, but they usually coat everything in a glass food safe glaze so it should be.
Unrelated, weed is legal where I live, so when I checked the website for the place I went, it had big banners for "summer kids clay classes!" And "pot-tery for adults!" right next to each other.
It totally makes sense but part of me is still startled by tangential consequences of legalization.
"Food Coma / Foodie" are in the image, and that's pretty solid. Maybe "3-Star / 5-Star / Greasy Spoon"? I like the one that you came up with that ends with "thanks Grandma."
These plates are a passive, very visual reminder. A tracker app requires you actively use the app, and not consciously/subconsciously underestimate portions.
Neither is a holistic solution, both require buy-in, each is going to have different effectiveness for different people.
I feel like there's a toxic body image/patriarchal component to only eating the large portion once you are a mother/soon to be a mother. Something about "letting yourself go" or something terrible like that