The Honda Part No is : 35881-S2A-911- The retail price is £52-42 inc VAT, but if you ask you can nearly always get 5-10% discount.
You will have to cut the dash a bit to get it to fit, it's not a straight swap for the lighter, but far better than the copies that are around and cheaper.
Wiring it up is not quite straight forward, but I hope to have a how to online soon.

BMW Z8 Starter Button	Honda S2000 Starter Button