Triboulet and Perkeo both in the Ante 4 Big Blind shop. You can get an invisible joker in the same shop, which will give a second Triboulet if you sell all non-legendary jokers. A Sixth Sense can be found in the Ante 7 post-boss shop, which lets you farm Spectral Cards using Perkeo to Death 6s, as well as holding negative copies of Spectral Cards that you don't want. Sock and Buskin shows up in the Ante 9 post-boss shop after a few rerolls. A red seal king can be found in the Ante 10 Big Blind shop in a Standard Pack. Brainstorm can be found in the Ante 11 post-boss shop, while Blueprint can be found in Ante 14 after a decent amount of rerolls.

Blank Voucher does not show up for at least the first 20 Antes, so I chose Black Deck for the extra joker slot, which lets you get away with holding the Sixth Sense for a long time.

The Plant also does not show up for at least the first 20 Antes unless you reroll the boss several times, but by that time you should have Retcon so it doesn't really matter.

Observatory shows up very late, so there's no chance for Perkeo and Observatory shenanigans.