Talk to the dwarven jeweler; you should be able to show him the picture you were given by the elf, and have him make a copy. Go through all the conversation options; I think after you ask him what he does, or something, he goes into how great a jeweler he is, and mentions being able to work from an image.
If you want a copy of the copy;
quick save the game, then drag an item out of your inventory, but not somewhere there is a red X. Without dropping first, quick load the game, then release the mouse button when it starts to load. This will produce a copy of the item on the ground, with the original still in your inventory.
