The cold cathodes are actually an item the almost any computer store will have. The most common use for them iin the configuration that many of us have in our trailers is actually to "Trick out" computer cases. (Why people do this is a mystery to me...)
The backlights in laptops are also ccfls, but they are configured differently.
The LEDs I use come from a small bidnez in Arizona.. the guy seems to do nothing but LED fixtures for both auto and home use.
Here is a link to his site (Which is sometimes hard to navigate.. keep plodding)
There are also many other sources in the helpful links Lighting,
but I have found these guys to be the least expensive, and most varied in product. They ship very quickly as well.
I get my ccfls off a supplier on eBay, they are about $7 a set, plus shipping, but the references in the links are similarly priced.