I want to purchase a custom copper island range hood that I believe doesn't come with the fan itself. Where can I purchase the parts for the fan and light system and how do I install something like this?
You can purchase custom hood inserts from a number of manufacturers. Your path to lots of information is to use a search in Google with range hood insert & blower unit.
One site that may be of particular interest can be found here.
Hood inserts are commonly available as many custom hood builders are craftsmen at their own art (copper, wood, stone etc) and not experts in blowers, filters and lights.
The most important thing you will want to do is to coordinate the design and build of your custom hood around a pre-determined hood insert size. Also place consideration for the control panel size, cutout and placement.