EDIT: I’ve located them. If anyone else is interested they are in:"…Steam\steamapps\common\Production Line\data\bitmaps\logos"
Also of note is that you can just create a new one(128x128 pixels .png file). There doesn’t seem to be a file pointing to only one, or the other, of the two currently available in game. Great news!
I would like to make a personal logo with Photoshop. I can just use one of the two that are in game and just paste over it. For the life of me I can’t locate the files. Any help is appreciated.