I am looking to downgrade my D7000. I am only able to find version 1.05, to my knowledge. It is somewhat confusing, but I don't believe I am able to find 1.04. Does anyone have a reputable and/or reliable source for a D7000 version 1.04 firmware file?
It depends if your camera is a Nikon D7000 A or B version.
Follow the link for the download.
In the above link, depending on whether your camera is ver-A or ver-B, the firmware will automatically upgrade. Unfortunately, for ver-A cameras there is no option of 1.05, and for ver-B cameras, there is no option of 1.04. (At least not that I know of.)
Your most likely chance would be to join discussion groups dedicated to Nikon or even the Nikon D7000 at sites such as DP Review, on Flickr (do they still even have such groups?), Fred Miranda, etc. and ask the members there if anyone had a saved copy of the firmware version you are seeking.
If someone does have the file you're looking for you would need to get them to send it to you. Then you would need to weigh the risk of someone you do not know sending you a piece of possibly malicious software against the possible benefit of rolling your camera back to an older firmware version.