http://www.ebay.com/itm/88-Tooth-Campagnolo-Nuovo-Record-Compatible-Chainring-/351292927541
This is a monster New Old Stock (NOS) 88-tooth chainring, the largest ever listed on eBay to the best of my knowledge, and I have been on eBay for more than a decade. It is in the Campagnolo Nuovo Record style (but is American made) and is 144 BCD. These are handy for long downhill bicycle races, while wearing full or partial motorcycle leathers and helmet “just in case.” Combined with a 13-tooth freewheel cog, this gives you an impressive 183-inch gearing (compared to 108 inches for a 52 X 13 setup). This means you move forward nearly 50 feet for every spin of the pedals. 110 RPM will get you up to 60 miles and hour on those long, steep straightaways, or on some well-lubricated rollers.
Or, if you simply despise your knees for some reason, you can try to start on the flats with this chainring.