Couple of places I recall which had such things are now gone or on hiatus.
However, here is one (sort of):
http://www.modthesims.info/download.php?t=195230It does require a mesh, which I
think is the floral one at the bottom of the page here:
http://www.xmsims.com/sims2/ehtm/mesh/accessoriesmesh02.htmAnd there is a complete outfit (dress, necklace/choker and veil) which accompanies the widow Sim on this page (free download, scroll down there):
http://sims2.simslice.com/sims2downloads-pg7.htmlUsing Clean Installer, you could install just the appropriate items rather than the entire large file of the complete Sim.