I am trying to locate Albert Kallo, Budapest, Hungary.  His Aunt has
lost his address.  Any suggestions?

A search for "Hungarian phone book" came up with this.

http://www.matav.hu/english/index.html

There are other sites too which might help. Unfortunately I got no
hits for Albert Kallo in Budapest, or indeed the whole of Hungary. Do
you perhaps know the name of anyone else in Hungary who might know
him? Perhaps you could find their phone number from the site.

Best