I got the manual from them, but that still leaves the manuals for Gaiden and the SNES games that I need to get. Anyway, I'm going to upload the manual to archive.org for preservation reasons, along with hopefully making it easier for others to find in the future
Edit: I uploaded the manual, and when I went to check the page it had the manuals for Mystery of the Emblem and Geneology of the Holy War as related things. I guess I didn't look there as hard as I thought, but after rechecking it I still couldn't find manuals for Gaiden and Thracia 776.