When I was a kid and used suits, when I started growing but my shirts still fit, except on the collar, my dad gave me this little contraption consisting on a silver button with a round spring attached to it. Oh, it dis save me from having my neck being tight because of the shirt.
Today while going through a drawer that has a lot of things in it I found it.
I haven’t used it in 40 years but it still works.
In the pictures you can see how to use it, and I bet it gives a half an inch larger collar on the shirt.