The Parry Shield's blueprint is found in the Stilt Village. The path to the blueprint requires the Ram Rune. You need a second village key to unlock the blueprint, so you should not unlock the door in the middle of the level. You must instead use the secret path above the door, which requires the Spider Rune or an amulet that gives extra jumps. The platforms required to make the jump may not properly spawn due to RNG, so it may require multiple tries.
Notes
This shield rewards aggressive play. Parried projectiles can pass through enemies no matter what shield is used, and the Parry Shield gives these projectiles extra punch.
The Parry shield is exempt from damage absorption affixes and is therefore more likely to get affixes that are advantageous to persistent parries.
Trivia
The shield still has statistics for block damage reduction & damage to enemies, despite its inability to do so. They are similar to most other shields.
Gallery
The platforms are high up, which can be reached by jumping from the building on the left.
The passage used to save the first key.
The breakable ground in the far right tower, which blocks the way to the blueprint.
The blueprint behind the door which needs a second key.