The Thrunite Archer 2A V3 will work as a single mode light if you want, the tail switch will only turn it on and off, $30 right now on amazon and can choose between cool white or neutral (I liked the design of the V2 better but can’t find it anywhere) This is a review of it:
https://budgetlightforum.com/t/-/42367
There is also the Manker E12 that has a tail switch that I think is only on/off, but I haven’t seen any reviews of it.
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This is a much cheaper option, Ultrafire C3 1 mode with extension (https://www.fasttech.com/products/1601/10000598/1057101-ultrafire-c3-1-mode-240-lumen-led-flashlight-w ) but it won’t be as bright as the others or as high quality so it may have machining defects, anodizing easily wears off, switch needs to be cleaned to work well, threads feel gritty, etc. Also I think its over 6 years old
What’s your price point? I’m not aware of many single mode AA lights except those with a side switch or twisting the head to change modes.