Anything led by Charisse Nelson-McIntosh from Richard Smallwood, anything led by Nee Nee of John P. Kee (I'll Serve Him, Pressing My Way), anything led by Timiney Figueroa (before she was Timiney Caton) of Hezekiah Walker, a lot of Milton Brunson songs (There is No Failure), a lot of Ricky Dillard songs have alto leads, as do most of James Hall's WAP and VOC. Tramaine Hawkins also leads a lot of alto songs.
You know, now that I think of it, I think you may be wrong. There are lots of alto leads out there. What kind of music do you typically listen to?