So technically by using cheats, we can give a flier the "Steal" skill and swipe his staves? Too bad I have already finished the game, that'll be looked into in my 3rd playthrough.
Oh that's dumb, cheating another Sleep staff is much easier.
In chapter 17A (Leonster's Gate), he appears after turn 10 and carries a Sleep staff and a Fortify staff.
I can't use Tina's Thief staff to steal his staves, despite her capped Magic and his Sleep staff is listed at https://serenesforest.net/thracia-776/miscellaneous/item-locations/