Yes. Try this site
http://www.kki.net.pl/sy99/sy77.html This site along with the one that you had will give you pretty much everything that I've ever seen available on the internet. And yes, all of these are files that you would simply put on a floppy and load up using the 77 disk drive.
I've got the SY77 Manager as well. I use it mainly as a librarian for all these different voices.
BTW, you may find that some of the voices on the site I gave you require a wave card. That's because a few of them are edited versions of the voices on a specific wave card. Most of them are not like this, though. Most are edited versions of the original SY77 sounds.