You might as well look for a 'Longsword of the Dynamo' in random loot. There are very few enemies that aren't effected by shock damage, plus the dynamo adds soul trap to keep it charged. You can get a glass one that's pretty good around lvl 16 or 17.
This is a great idea, but just a teensy bit off in the detail. Dynamo simply adds 15 points of shock damage.
http://www.uesp.net/wiki/Oblivion:Longsword_of_the_Dynamo#Longsword_of_the_Dynamo
There are random loot enchanted weapons in the SI however, such as 'of Soul Voltage' that combine 15 points of shock damage with 5 seconds of soul trap and are available at level 11.
http://www.uesp.net/wiki/Shivering:Dagger_of_Soul_Voltage#Dagger_of_Soul_Voltage