Zig's weapon shop 100% impossible to exchange.

Seems like I cannot exchange any of those powerful weapons since many of the required items were removed from the game. I swear that I am not lying. For one, Void Erebite Fragment doesn't exist. There is no way to get them.

You need to farm the hell out of the Persona UQ or triggers for Void fragments, I have a full set of Trailblazer 2 units and three Trailblazer weapons from countless runs with that boss.

I believe I may saw them with Sirona - Treasure Shop Trustee few times. I think she was offering them for meseta. Keep an eye out on the shop.