Don't know who sells them now.
I bought some about 15 years ago and they work pretty well (I think they were made by Challenger then but I could be wrong). You will see a very small flare indicating the path of the shot string. They work better on overcast days or nearer to dusk, not so well in bright sunlight.
They recommended on the box to use in damp\wet conditions (for example - after a rain is perfect, or near dusk when there is dew on the grass) so the ground is not dry and you wont start a brushfire. The flare is pretty small and i think the fire risk would be minimal.