Neal is spot on,. I've made up a number of them in the past; I wouldn't bother with the expensive Spekky one, Maplins do what you want for pence and they are easy enough to solder up. When I get a second I'll dig out the Maplin part number, but basically it's a 16V 4700mF radial electrolytic capacitor. Just make sure you wire it up the right way round (+'ve to +'ve)... if you get it wrong you'll get a real nice 'pop' at some point! they don't like it up'em
