Being an Arcane Archer is supposed to be exceptional as-is - it's unlikely that there'd be a generally-known way to make an AA-specific bow. It might be the subject of a CDQ, or an extremely-rare-dropped-item, but given the scarcity of the PrC, it's hard to justify that kind of development. (Given that Kell's still got his hickory bow, I've really no opinion either way on this. *chuckles*)