I can only share experience with what worked for me. I use a Nitecore NU25,
NU25 - Nitecore Australia. This is not advertised as a dedicated astro torch, but one of the suitable activities. It has a dedicated button for the red light. The red light has 3 modes in this order - dim, bright, flashing and you can power off from each mode, so no need to cycle through. It's rechargeable, so I can hook it to my power bank if needed. If only using the red light, it lasts ages.
PS: I see today these are considerably more expensive to what I paid 2-3 years ago. There might be better value/feature offers available.