If you’re looking for an inexpensive (around $10) rifle torch/flashlight then the UltraFire WF-501B is worth considering.
I have both the red and the white emitter versions. The red one only reaches out to about 20-30 metres, but because of the colour it means you can generally get pretty close to whatever you’re after. 30 metres is about the maximum distance you can get a solid ID on anything, but you can clearly see eye reflections out to 100 metres. I use the red one on my low powered air rifle for rats in the machinery shed, and on the 22 for rabbits that come too close to the house. It’s also good for just walking around at night while retaining your night vision.
The white version has significantly further throw, out to 50-75 metres. I use it on the 12 gauge for rabbits and foxes out in the paddocks.
All the WF-501B’s are single mode, so you’re not going to accidentally go into strobe mode. You press the button it turns on, press it again and it turns off. You can buy them with or without a pressure switch, but since the pressure switch only costs a couple of dollars extra it’s worth paying for, even if you never end up using it.
The WF-501B takes 1×18650 battery, and the tube diameter in 1″, so it will fit in most scope mounts or dedicated flashlight mounts. They’re also available in green, UV, and IR. You can buy the different emitters individually if you want to swap them out, but the whole torch is so cheap you may as well just buy a complete assembled version of whichever ones you want.