All 1165 characters are provided in two typefaces, regular and boldface and can be accessed by their syllable names.
And finally the zipped archive: The Yi 4 LaTeX2e package
If you want to see some of the classical Yi characters together with a few modern ones (plus phonetical spelling), then you should not miss The Yi Script by Lawrence Kwok Leung Lo.Oliver Corff, Ulaanbaatar, September 1997