KK 4000 protected from CNQ might be a good option. Never seen a test on them. But expect performance like KK, but generally 0,1V lower voltage due to protection circuit. Battery length might be an issue?
There is also the Soshine 26650, but they are probably not as happy with high current+ as the KK. Id guess they are out due to that. They were testet here. They are very long too! In that same thread some IMR cells were mentioned. Those might be an even better option than the protected KK for your light (but then there is obviously lower capacity).