What about this strobe light (not a LED model) ?
If you can find that brand in the US of A.....

Approx. translation of the text :

Flashing marker.
Manual activation.
Fastening : stainless steel clip, on the back of the unit.
Activated by turning the rotating ring (bezel ?), around the lens.
100m waterproof
Visible at 3 nautical miles
CR123 battery included.
Weight : 100g (without battery)
3 functions :
- constantly on (battery life = 4 days)
- flashing (60 pulses per second) (battery life = 8 days)
- S O S mode (battery life = 8 days)