wall sconce question

Hello,
I'm currently gathering ideas for a bid of building several stained glass
wall sconces. Is there a source for the guts and backing of such a lamp
where I could simply attach my own front panel or would it be better to
purchase some from my local hardware shop and remove their panel and insert
mine? I'm looking at creating something about 6" high by 13". Have any of
you built this type of lamp before? Any advice would be helpful.
Thanks.