I purchaced mine from elect2go -
http://www.elec2go.com.au/EL-panel-p/k.a3.w-o.htm this is a A3 size.
There are 2 issue to look into when getting into EL blacklight.
1 - Light distribution. I used a pearl perspex panel to enoure the light was evenly distributed. Just in case senario.
2 - More complex is the potential for loops in the power supply. As they are high voltage they have switching power supply that generates fairly large EM field. This can be induced and/or loop into cabling and appear on the image as bands of light.
I am still experimenting although have stopped at the moment due to the re-build of my obs.
For the moment I am shooting flat on a clear blue sky until I get my rig set-up. Which is the simplest method.