Well...-scratches his beard- i'm not entirely sure why your looking for one...but I suppose I can toss out a couple ideas, I dont know about their safety so becareful Buuuuut....

You could attempt mixing like water with some sort of hot sauce, or like....jalapeno or habenero pepper juice. I suspect on a sensitive region that would cause a great deal of discomfort.

Id also say that if you decide to go that route, I don't even know if it would function, but keep milk on hand to administer a follow up if needed as that should help to clean out the oil residue from the peppers.