Broken Bat Wing

It only comes off Vampires, so you need a Solar Eclipse running, and eclipses do not turn up on a schedule. What limits you is how many Vampires actually spawn during one, not luck on the roll, so park a Water Candle in your arena and drink a Battle Potion before the sun goes dark. More enemies per eclipse is the whole game here.

You can build them much earlier than the recipe suggests. Temple enemies spawn outside the temple as soon as Hardmode starts, so the Solar Tablet fragments they carry can be assembled and an eclipse forced before you have killed a single mechanical boss. At that point nothing else in reach flies better except Fishron Wings.

If you are only after coins, finish the wings and sell those instead of the parts. The assembled item is worth considerably more than what goes into it.