Is there any information, apart from the three games, regarding Fischer playing the Greenblatt computer in 1977? Wasn't Fischer living in seclusion at that time? How did someone manage to have Fischer play? Is there any photo of the event?
TL;DR: In summary, the sources I've found of the match reference Fischer himself.
Fischer sent the game scores himself:
Rumors constantly reappear about the possibility of his playing again or making public appearances, but the only published games that we know of since 1972 were against the Greenblatt program, and they were submitted by Bobby himself and published in the Computer Chess Newsletter. Bobby sent the scores of three games in which he massacred the computer. In his comments on the games, Bobby noted that the computer was very weak and that he could give it great odds and still beat it.
The match was held in Cambridge, MA:
In 1977, unbeaten chess champion Bobby Fischer played three games in Cambridge, Massachusetts against Greenblatt's computer program, and Fischer won all of them
Source: Wikipedia, referencing Bobby Fischer's biography
I haven't found contemporary images or information on how the match was arranged.