Having a decent focus light can greatly improve your photography, particularly when shooting macro. The camera locks focus much more quickly and yo can see the critter and frame faster and see your focus point. If you're just using one strobe, then using another arm works fine to hold a light. But if you use two strobes, how can you mount a light, if your housing doesn't have a built-in mount?

Enter Fantasea Line's Port Mount Bracket. Available in three sizes (92, 101 & 104mm) to fit the ports on their DSLR housings, I've adapted it pretty easily to fit my Ikelite Fuji F810/E900 and similar compact housings that use the Ike lens adapter for Inon external lenses. Other housings that have a port with a wider, round shape probably would work as well.

The mount justs fits nicely over the lens mount. You do have to cut it down and re-drill about a 5/16" hole carefully. Clamp the strap down on both sides to a piece of scrap and drill a pilot hole first. Not hard.

The LED44 is a great LED light with a soft, white wide beam. It uses 5 alkaline batteries (I don't recommend rechargeables) and lasts for several days of shooting, like 12-15 dives.

I don't use the Ikelite flash blocker. It is very awkward and falls off. I use a Fantasea optic cable that velcros on the front. Then I just tape off the inside of the housing with tape except for a small area where the cable attaches. You cannot use the internal flash with the lens adapter it results in a big shadow.

There's a few more photos here.
I have the parts for sale as a package:
Fantasea Line LED44 and Port Mount Bracket Package.