I have looked on kaggle.com and done a lot of Googling. The only thing I found was one that has 2000 vertices in the polygon for each province. That is too large to write to DynamoDb, which is what I need to do.
there are many, but this one at 398 kb should probably work.
It's not "official", though. For official, you'll have to make your own geojson from here.