I have used the small LED lanterns. You can buy them at Walmart in the camping section.
Any sporting goods store should have them. They give you 360* visibility.
Just attach to the top of a piece of PVC with a screw and some adhesive.
You can go to bckfc.org and look under the rigging section and do a search for
lighting, etc.
This is the site for Bayou Coast Kayak Fishing Club...lots of kayak info here as well
as fishing info.
Any of you guys that use a kayak should check it out.