Try this or any other marine flare suppliers of parachute flares. Just don't use them over water.
4 Calibre Parachute Flare - Aluminum Case
Catalog #6325 Burn Time: 40-45 seconds List Price: $40.00
Altitude: 120 meters, 10 cartridges per box. Visible from a distance of approximately 4 KM by day and 40 KM by night. Colors: Red, Green, Yellow or White. For use in Heckler & Koch Signal Pistol (P2A1).