Take a look at the Fantasea Remora Strobes for $189, has preflash control, variable output and a DIN 14 rating on power.
The Ikelite housing for the G9 is cheaper than the G10. Ikelite has a new wide angle lens for the G10 that you can remove while underwater. I always worry that my Canon housing will leak but not with my Ikelite housing for my point & shoot S80.