See For Sale - SEA & SEA YS-D1 Underwater strobe. Used..Yeah... The Backskatter Hybrid Flash--although not as expensive as some of the options out there--is a little out of my budget. I was thinking $500 max, including the batteries and fiber-optic cable. I think I'll probably take @tursiops' advice and buy a good used strobe.
This is a good deal. I have two of them.