To add to RudeDawg and Accord's Staff of Striking suggestions, there are a few of these in the game, so you won't miss out on this one item by not doing the Drow city (although of course they are charged items and will eventually run out).
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There is another on sale at the Temple of Lathander (Temple District, Athkatla)

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Time is an illusion. Lunchtime doubly so.

Epona of The Laughing Hyenas and The Ladies Guild.

The merchants also have the Sentinel Shield +4 - most tasty!

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And I remember Adalon, the Silver Dragon, has a Light Crossbow +2 to give you if you can get her eggs back... good fun, if you like that kind of thing.

Tancred

"A Crossbow?!? What the Otyugh am I going to do with a Crossbow?!?"
- Tancred, a peeved Cavalier

I suggest after robbing the drow blind KILL THEM ALL! AH HA HA HA HA HA!

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Bruce The Aussie, Camp Barbarian Hunter OHF
jester of LH and Master Beastmaster of the clan of the Kats