Raymond,
there are many suppliers of EL panels - check on Ebay, web, etc. Our region purchased a large number from a company and then passed the savings on to the users. I messed around at one time about bringing a lot of these over from Hong Kong but never did it.
One issue with EL panels is photodegragation. Over time UV light will break the double bonds making up the polymer and degrade the material. This will appear as dark spots on the panel and uneven light output. Eventually the they will fail. Humidity is also to be avoided with the panels as that will damage them as well. So, you probably don't want to leave them on the car all the time.
EL panels are fine for occasional use but they can get mechanically damaged as well. One of the sets I made for my car before the VIR enduro group mandated them was damaged by a stone or rock in practice before night testing. The film was pierced and created a short in the panel. So, when we turned it on for night practice the short burned up the inverter providing the high frequency AC for the panel and we were out of luck for using it for the race.
The panels we used this past year, the ones the region supplied, we covered with clear tape to add an additional layer of protection.
I used to have a file with a lot of different EL suppliers but I don't have it any more. Many of the HK companies were more than willing to send samples for evaluation. Also, you'll find the green and blue panels to have a far higher specific brightness than the longer wavelength panels (>530nm). In many cases the longer wavelength panels have to use an intermediate fluorophore that absorbs the blue/green photon and re-emits a photon and a longer wavelengh - deeper green, orange, red etc. This process is inefficient and you notice it as a panel with less brightness.