I've done that once before... it requires a little luck, but if you got the Nazar Pre-Plantera, and it helps if you found a Bezoar in Pre-HM Jungle, the other parts are really not that hard. The worst is the armor polish IMO, because blue skeletons outside of the HM Dungeon are rare.
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Xylia
652Graystripe
My last one was the adhesive bandage - no full moons to speak of, and angler fish aren't the most common things.
Xylia
Yeah, I try to time it so that I enter hardmode 1-2 days before a Full Moon.
SnailsAttack
what the 
how
how
Xylia
It's rather easy... Nazar from Pre-Plantera dungeon, Bezoar in the Jungle pre-Hardmode, Megaphone from Pixies, Blindfold from Dark Mummies (or dark slimes), Bandaid from Angler Fish or Werewolves, Vitamins from either Corruptors or Ichor Stickers, and Armor Polish from blue skeletons.
Xylia
None of these mobs require the mechs to be defeated to get their drops. You just need some water candles and some patience with a little luck. And biome manipulation. As previously mentioned, the armor polish and bandaids are usually the hardest to get.