Try Wideners.com or
google wideners reloads or the size flares you need for your gun. The 26.5 mm are supposed to climb to 1000ft. They are surplus and one seller tested them and had 100 %
work. They are military grade with no experation date come in different colors, parachute, and smoke. I think the reason for the 25mm was so you can't use the 26.5 flares, they would have had to make a stronger pistol.