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Yep, your two choices are the 1SM-2 and the 3SM. The 3SM delivers more current (1.2 amp) to the LED than the 1SM-2 (1.0 amp), so it will be a bit brighter, albeit with a corresponding shorter runtime.
So, if you want 3 output levels, you're in luck because that's the 3SM.. the brighter one. If you really only want one level, you'll have to give up a tad of brightness. Will you really notice it?...nope..unless you have the eyes of a lux meter.
The 1SM-2 also gives you the flexibility of using an 18650.