That kind of hat is called a "peaked cap" - that keyword might find you what you want quickly.
You could also search things like "cop hat" or "army hat" (even if it might not be 100% correct) to bring up really cheap Halloween costume type stuff depending on your budget.
Disclaimer : This post written by a Grumpy Old Man
Actually in the pipes:
- Remaking Ser Loras doublet.
- Luke Skywalker, A New Hope
- Wind Waker starter costume in swim material
Eventually: Paul from Dune, Faramir, Harry Sullivan