you have to have the Bonus Merchants installed. it gives you Joluv in the Coronet, who has good stuff, and Deidre in the AMart, who has incredible stuff. (Vecna included) download it from
Baldurdash and you will not be disappointed.
The shield itself is only useful against beholders. it reflects their rays and gives an AC bonus of 4, but gives a -1 to strength. it's good for the Unseeing Eye, though.