MIC p.42
Glad I found it. DM shot down Spell-Storing arrows and I have Torch Bug Paste but I try to stay ~100ft. or so away from the action.
The gnome calculus (A&EG) could let you throw the torch bug pastes that far. It would be a bit cheaper, and you only have to hit a square adjacent to them (not a direct hit, like the arrows). It's good to know about the arrows, though. I'd not noticed those before.
There's also the Weapon Crystal of Revealing that does the same thing as the arrows, and can be swapped between weapons. I believe the Least would work.