This is a quick replacement door i designed for better airflow to the ram and nvme ssd's for the Ugreen DXP6800Pro nas. It might fit the other models as well, i'm not sure if the door size is shared or not.

I designed it with the intention of adding a Noctua 92x15 fan on it as well, but to do this you have to raise up the nas a bit. I've designed feet as well, but I have not printed them yet or tested, but they should fit well and will raise the nas up to the correct height.