you can buy those sinker weights made for fishing live bait. they have the little rubber things in em. let me see if i can find a picture.
ah, rubber core sinkers.

http://www.tacklewarehouse.com/descpage-WGRCS.html

they sell em at most tackle places and come in different weights. what you want to do in your situation is take out the rubber piece in the middle then if the weight will fit over your desired hook then put it in and clamp it shut with some pliers. If it won't fit you gotta open the weight up a little with some pliers.

or just buy premade hooks with the added weight already on em.
for customizability though you can't beat the rubber core sinkers.