C. Striatus, the Banded butterflyfish, is among the most common butterfly fish in the Caribbean. They are numerous along the S.E. coast of the US from Florida to the Carolinas, and I always catch a few Gulf Stream strays in late summer/fall here in NJ, as do collectors in Connecticut, R.I., and N.Y. They are less numerous up north than Spotfins and Four Eyes, but most summers I catch three or four.
I see more Banded BFs on most shallow Caribbean reefs than any other BF species, almost always in pairs. Small ones are very similar to small Four Eyed BFs. Four Eyed BFs lose the bands at about an inch.
I think they, along with most other Caribbean BFs, are difficult to feed unless you have unlimited access to live blackworms. They can be maintained, but a lot of effort is required to keep them healthy until they accept the usual aquarium foods. Large ones are nearly impossible to keep successfully. I've been able to raise just a couple of these fish. Spotfins and Four Eyed BFs are much easier. Not very much comes out of the Caribbean these days, and valuable shipping space goes to Angelfish, Grammas, etc. There are a couple of collectors who sell directly via the internet, and they always have Banded BFs listed. They are common in Florida, and not expensive. Any decent local shop should be able to get you one. Get a small one.