I bought one of those fitted baseball hats. I really loved the design, and really wanted it. It fit, but varely. I mean I can wear it, but it would be perfect if it could be just a smidge bigger.
Does anyone have any suggestions on how I could stretch this hat ever so slightly?
Wet the cap first and then find an appropiate size bowling ball to stretch it over.
I thought about wetting it right away, but then thought “Isn’t that how laundry shrinks?”
Put it on, then we’ll all say really nice things about you. 
Not sure what it is made of but many materials will stretch if you hold them over steam and then apply pressure while it is still hot and wet.
Not as long as you have a rigid form inside of it to keep it from shrinking.
There is a gizmo called a “Hat Jack” specifically for stretching hats. I got mine in the US, and have used it on a couple of straw hats that’ve shrunk. It works fine. I suggest you google “hat Jack” .