Hi trigger,
Unfortunately, your Bonica strobe will not work with the OlyC4040Z because of the pre flash issue. Actually, some digicam comes with preflash and some don't, the Oly c4040z has a pre flash features which measures the available light prior to exposure. I have a feeling even if you managed to make the Bonica strobe fire, the timing will be completely off. The Bonica strobe will probably fire even before the shutter opens resulting to poor lit image.
There are several strobes in the market that will work with the olyc4040z. As Dee mentioned, there's the Sea and Sea YS()DX, Ikelite DS50 or DS 125 or the INON D-180. I have not used any Ikelite DS strobes but I have used the Sea and Sea YS90DX. The YS90DX comes with a lot of cool feature like the 12 step lighting adjsutment, strobe comaptibilty with either MotorMarine, Nikonos or any housed SLR that comes with a five pin sycn port. You will need a fiber optic cable kit for the Ys90DX to really sync it with the internal flash.
Hope this helps.