I hate to say it (I know it's a discontinued strobe) but if push comes to shove, make one? It's easy enough to do and also easily adaptable from the land flash version on that site. No, it's not as perfect as a proper tailor-made one, but it'll do.
I'd add a tether to it because you'll otherwise inevitably lose it. A simple hole preferably outside the working bits of it with a figure-of-eight knot on a bit of string (light cave line?) which doesn't float attached to yourself wherever you find convenient does the trick nicely.