Heater Shield is crafted with Blacksmithing in Mabinogi (shield). This page lists everything needed to make it, checked against the game as it exists today. The interactive planner lives in the Blacksmith Companion.
How to get the manual
The manual is rank 6 and survives 30 uses; every crafting attempt spends one use.
Fossil Collection Book Vol. 1: turn in restored fossils to Belita for a collection-book reward. Buy the book from Belita; fill it by restoring fossils mined in Zardine via the cleaning minigame.
Materials
Expect about 4 attempts per finished item (26% average progress per attempt). Per-attempt materials are consumed on every attempt; finishing materials once per item.
Each attempt uses
3× Iron Plate — refine from Iron Ingot (re-refining)
3× Mythril Plate — re-refine from Mythril Ingot
Finishing (once per item)
3× Fine Leather — fragmentation of Fine Leather Strap (or weaving byproduct)