Tiphia Sting maybe? Probably the cheapest and best alternative if you don't (understandably) want to fork out for a Black Tathlum.
As for making a mule and completing the quest, as far as I know (from a friend, but this may or may not be true as I haven't personally tried it) you need to be a certain level to flag the quest, which means you may need to level a mule up to get one.
could still get it back with SE recovery of 1 Item (and only one item) if its worth that much for you. But me personally wouldnt waste that 1 possibility to get item back for a grenade. Think Tiphia is the only thing all 3 listed jobs can use as a cheap replacement. Otherwise if Bomblet is too much for you just for DRK can get Bomb Core.
I'll sell my smart grenade for 3 mil on Bahamut if you threw yours accidentally. Personally, I fear I will do the same thing, because I do so love my /rng. It'd be better to get it away from my idiotic fingers :) Any takers lol?
Sorry to hear that happened. Personally I would try to request the item with a mule, or maybe try for those NMs that offer alternative items for that slot.