Alarm Clock
Where to get it
Alarm Clock can be found aboard the S.S. Anne in Bleak Beach (golden Pokéball).
Crafting
Tool: Workbench
Materials: iron-ore x1
You can find it in the S.S. Anne in Bleak Beach, or craft it. Game8 lists a craftable version requiring Iron Ore x1 at a Workbench.
Source: Game8, community