It might be the size of the cap badge that may be throwing you off. I use to wear a large pewter badge I picked up along my travels, but I always thought it looked too big. (Even though it was sold as a cap badge) I bought a smaller silver hallmarked pin and replaced the large pewter one. I think it looks better.
Here are some photos:
Old badge:


New badge


Detail


(As a MacArthur, you have probably noticed that the new badge has what is know as “the battle cry” rather than the motto. I had never seen one like that, so I had to have it!!)
Wear your new bonnet in good health cousin!
Sara