Here is a .dds file made out of your sky texture. It looks good in the cubemapper, FX composer and Dark Shader. I can't say it will look okay in your program because I can't test it. If it doesn't look good, all I can say is have a try at making it yourself. The programs I use to make cube maps are HDR Shop version 1 and ATI Cubemap Generator. Both are fairly easy to learn and both are free.
You can get the cubemapper from ATI and for HDR Shop just search for in on the web. Also you may need microsofts texture tool (available in the Direct X SDK) for changing the texture format.
Good luck and if you have any questions I'll try to answer them.