Historically ninjas could make "black eggs". They normally had glass in them. I want to represent this as mundane item. I can't think of a price though. The Fort save will be a 15. If there is already a similar item(pathfinder or 3.x) I would take its stats.
Dust of Sneezing and Choking
This fine dust appears to be dust of appearance. If cast into the air, it causes those within a 20-foot spread to fall into fits of sneezing and coughing. Those failing a DC 15 Fortitude save take 3d6 points of Constitution damage immediately. Those who succeed on this saving throw are nonetheless disabled by choking (treat as stunned) for 5d4 rounds.
(cursed item made by botching another magical dust. In the original SRD, however, cost 2400 GP sale price and required the "poison" spell).
That sounds like a "black egg" to me.
The Oriental Adventures (3rd edition) book has black eggs as a mundane item.
The dust of sneezing and coughing does more than what I want it to do, but the eggs in the book are just fine. I can't believe I never noticed them, especially since I was looking for them. I will probably raise the DC to 15. Thanks.