Search digikey com for supercapacitor There you will find a number of capacitors listed in the 1200 F to 5000 F range At this moment they offer 1700 F 2 7 V for 160 3500 F 2 7 V for 210 and 5000 F 2 7 V for 255 These are made by NessCap Co Ltd So they do appear to be available though I would not say that this is an indication that they are widely available