Hi Kandace,
The Olympus pt 020 housing is equipped with a bulkhead that will support an Olympus strobe. It should be noted however that the strobe was designed for top side use. imho, the strobe (FL 20) lacks features that would make it a serious tool for underwater use other than possibly macro subjects. I do not believe it would have the power necessary to cover the field of view of even the native lens of the c5060 at Wide Angle focal lengths. Even more concerning to me is that there are reports that spare parts, including important replacement sync cords, are very hard to come by.
If a hard wired system is your preference, you may opt for a mike-dive.de replacement bulkhead system. This would allow you to maintain Olympus TTL control of an external strobe if the strobe you choose incorporates a standard Nikon sync connector.
As james points out, optically triggered strobes are much more common in use among the many divers who visit wetpixel who share your system (c5060+pt020).
An optically triggered strobe is one that gets it's signal to fire from the onboard (or internal) strobe of the digicam, through a clear housing. the external strobe may pick up the triggering signal in different ways. Inon, Sea & Sea, and Epoque utilize various forms of fiber optic systems. Ikelite uses an optical sensor attached directly to the external strobe and aimed at the onboard flash. And some external strobes rely solely upon a sensor built into the strobe head.
The optically triggered strobe may be controlled in one of three ways, some form of TTL, Auto, or Manual. Each strobe control method has it's supporters. Many strobes are capable of more than one type of strobe control. Some combine Auto with Manual. Some TTL and Manual. Some can even accomplish all three.
There is no one "best" strobe for you to choose. James made mention of the Strobe Finder. Along with a multitude of specs and data you'll find there , you'll also come across some simple explanations to help you wade through the plethora of choices. Your choices could be dwindled down by the wide variation in price. You could also narrow the search by defining how you wish to trigger the strobe. Your camera is capable of both emitting a preflash or sending out a single "slave" signal.
My advise at this time would be to have a swim over to the database:
http://www.digitaldiver.net/strobes.php
and when you're ready to come back up for air, swing by with a couple of more specific questions. Maybe even narrow it down to three or four strobes. If james is not around, someone else will be here to lend a hand.
regards,
b