Below you can find logos, similar to the sigg.

Siggraph 2001 Siggraph 2001 vector
Siggraph 2002 121 Siggraph 2002 121 vector
Siggraph 99 Siggraph 99 vector
Acm Siggraph Acm Siggraph vector
Siggraph 2000 Siggraph 2000 vector
Acm Siggraph 30 Acm Siggraph 30 vector
Sigg Sigg vector
SIGGRAPH 2000 LOGOS SIGGRAPH 2000 LOGOS vector
Siggraph 2002 Siggraph 2002 vector