With this mod you can create a customizable farmsign. You will find it in the Misc category of the vehicle shop (not in the buildigns shop!)
The sign costs 500$ and customazation options for text/color are free.
Currently it is customizable with some options in English, German and Dutch.
Are you missing some text for customization, or your language? I will open a topic in the Giants forum where you can leave requests.

Note! If you have trouble placing the sign: make sure you have turned it (kind of) straight and then make sure the feet touch the ground before releasing it.