I see that two Lucas biographies differ on when the Supersnipe investment happened.

http://books.google.com/books?id=M6OKPBLep0gC&q=%22george+lucas%22+supersnipe&dq=%22george+lucas%22+supersnipe&hl=en&sa=X&ei=9vwmT9j_GoyCtgenzZEl&ved=0CEkQ6AEwAw

Empire Building pg.51 [talking about the aftermath of Graffiti]

Lucas indulged himself by buying a stake in a comic-book store, called Supernipe, in New York. Otherwise he remained the son of George Lucas Sr.

http://books.google.com/books?id=G4A5djW95UsC&q=%22george+lucas%22+supersnipe&dq=%22george+lucas%22+supersnipe&hl=en&sa=X&ei=9vwmT9j_GoyCtgenzZEl&ved=0CDcQ6AEwAA

Skywalking pg. 193

Lucas allowed himself a few guilty pleasure: he invested in Supersnipe, a Manhattan gallery that specialezed in original comic strip art, and bought a Ferrari sports car. It was, of course, a used Ferrari.

http://books.google.com/books?id=h5IYAAAAIAAJ&q=%22george+lucas%22+supersnipe&dq=%22george+lucas%22+supersnipe&hl=en&sa=X&ei=9vwmT9j_GoyCtgenzZEl&ved=0CE4Q6AEwBA

H.W. Wilson Company - 1978 - Snippet view [pg 260]
In addition, Lucas has invested in Super-snipe, a Manhattan art gallery specializing in comic book art. ... he admires in Lucas his singlemindedness, his perfectionism, his sensibility, and his "gift for popular narrative." George Lucas ...

The person to track down is this Simon Dietrich, who did the day to day operations. Not finding much substance, could ask http://www.fantagraphics.com/ as some of his work goes thru them, or contact the brother who seems to have a bigger following, and might be more public.