I'm trying to make a set of filled soul gems be a respawning stock at a vendor so I can buy a supply of filled soul gems. Any ideas as to how to accomplish this? I have a working knowledge of the construction set, I'm mainly looking for a way around the fact that you can't fill soul gems unless they're in the game world but if they're in the game world then there's no way for them to be respawning or for me to buy them off a vendor.

in this mod, npcs enchanters may sell you filled soulgems. If you want to have a look, ask them about "My trade". Then the topic "enchanter's services" should be added.
http://planetelderscrolls.gamespy.com/View.php?id=5892&view=Mods.Detail