Ive seen HDMI/DVI/VGA/USB extension cables that are 10-15m in length here in Seoul (I know it doesnt help). My point being they should be available somewhere.
You can also get cables custom made as well. Also, you may lose signal strength/resolution over such a great distance. I sometimes lose USB signal using a 5m extension.
Lastly, can you SEE that far without eye strain? I had trouble seeing my display on my old 40" lcd setup @5m lol.