Here's a replacement key for meter boxes. I don't know what countries these are standard but at least it works in Austria. Maybe even EU wide? Anyhow, there's a number on the original key “61005” that might help in identifying.
I made one side slightly flat so you can print the overhangs without part cooling fan in order to ensure strongest possible results. You'll still need a tiny bit of support for the key bit though.
Made mine in Fabru PC filament and it seems to keep up the load quite well, even with just 30% infill. Make sure to use some strong and stiff material or otherwise you could ruin your lock with it.
The author marked this model as their own original creation.