If you can't obtain an ofuda or gofu from a local shrine, or from a shrine of your preferred kami, you can use this 'fuda generator' to create one for your kamidana.
Select the name of your kami from one of the dropdown lists below.* Using a color printer, print the page on heavy cardstock 65 lb. When it's done printing, cut along the gray lines and fold in half lengthwise.
After you purify and bless it, your ofuda can be kept on your kamidana in a plastic sleeve on a stand, in a covered box, or in a miyagata
You should replace your ofuda at the beginning of the New Year, and either return the old one to the shrine from which you obtained it, or ritually burn it on January 15th.
If you don't see an ofuda for the kami you're looking for, us and we'll see what we can do about adding it to the lists. Please note that we do not list specifically Japanese kami; you should be able to obtain these from one of their shrines.
* We don't recommend using the last dropdown list for your kamidana; it was included for those who might be having trouble, and wish to calm the kami on that list.