We don't have synonyms for a propos yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are apropos, atropos and aprosos.
"apropos the return home of the body of old King Nicholas of Montenegro ('Communists allow burial of Montenegro's last king', 2 October): King Alexander of Yugoslavia was his grandson, not his son-in-law."
"apropos the return home of the body of old King Nicholas of Montenegro ('Communists allow burial of Montenegro's last king', 2 October): King Alexander of Yugoslavia was his grandson, not his son-in-law."