It seems that 50-Farad 22Ah ultracaps are in the marketplace now.
http://www.echo-electronics.com/blitzbzcap50050faradamplifierstyledigitalsupercapacitor-p-1076.html
http://www.amazon.com/AROUND-INDUSTRIES-PLCPBT50-Battery-Capacitor/dp/tech-data/B000E3V9FS/ref=de_a_smtd
I couldn't get much...