Here are the turn signals I use.(They are very Bright too)
I am a V-TWIN dealer.You should be able to get them any aftermarket HD shop.
http://www.vtwinmfg.com/webapp/wcs/stores/servlet/CatalogSearchResultView?sto...The brackets are the stock brackets on the front.I made the rear one.Found some hollow tubing at the local hardware store.Bought a tap the is the same threads as the turn signals and tapped threads in it.Welded tabs on to match the fender mounting bolts.
I like the dual elements.On the rears I run them as brake lights on the dimmer side and turn on the brighter side.Along with the regular brake lights.