I did it just as explained on the geck wiki, but it won't allow me to save it. I understand that that is due to some error within the script, so I'm posting this here so someone with more modding experience than I could diagnose this.
scn AddNeckChainScript
begin gamemode
additemtoleveledlist VendorMiscItems Fechain 1 1 100
stopquest AddNeckChainScript
end