Yep, hydrogen sulfide is definitely something you need to take seriously. Whenever there's a risk of workers in industrial processes (in Sweden at least) to be exposed to it they have to wear detectors that warn when the concentration exceeds a certain level.
If you are exposed to very high concentrations, you can fall into a coma after just one breath. It is pretty fascinating how fast the body transports substances when they are absorbed through the lungs.
Luckily, for the purpose of making stink bombs only low concentrations are required and these can be tolerated indefinitely by humans as our bodies have a very effective way of dealing with hydrogen sulfide. The recognition threshold is as low as 5 ppb and since the olfactory sense is generally saturated at concentrations 10-50 times higher than the recognition threshold there's really no need to go above 1 ppm. Such a concentration would be harmless (apart from the smell) to humans.
However, to reach 1 ppm in a 5 x 4 x 2.5 m room, 68 mg of hydrogen sulfide would be required (assuming homogeneous distribution). If this was released in a much smaller volume, say 0.5 x 0.5 x 0.5 m the concentration would reach 400 ppm, which can actually be fatal. For this reason I highly doubt any commercial product releases more than 10 mg and the actual amount is likely to be around 1 mg.
To make your own stink bombs I would suggest using zinc sulfide which can be obtained as cheap glow-in-the-dark pigments and hydrochloric acid. Both should be available at well assorted paint stores. Be careful though, as 1 g of zinc sulfide will produce 350 mg of hydrogen sulfide.