If you find a single-D-cell version of the strobe, designed to attach to a life jacket with a large safety pin on the side of the case, a bit of hunting should find a replacement amber dome for it. The amber dome is intended to somewhat reduce the damage to the user's own night vision while maintaining long-distance conspicuity. But it would also have the advantage of being legal for vehicular-warning use. I used one of these for commuting in the fog many years ago.

If you don't need the battery life of a D-cell, there's also the single-AA-cell "Aqua Strobe" rated at 8 hours life. I don't know if they sell an amber dome for it.