In order for the flashlight not to warm up to 1000 lumens when constantly turned on, as
@Hooked on Fenix said, it must have a lot of metal to dissipate heat. This one definitely won't get very hot at 1000 lumens:
Mateminco MT90 Plus
But it has its drawbacks - a lot of weight, a very narrow beam.
Most flashlights now have good thermoregulation, you may not even notice how they drop from 1000 lumens to 500-600 while remaining a little warm.
It's better to write us additional wishes - size / weight, type of beam (narrow, wide or medium), light color (closer to incandescent or cooler shade), then it will be easier to pick something up without going to extremes like me with Mateminco MT90
Example Nitecore TM26, there was a graph in the 2013 review, at 1700 lm it worked for a little over an hour and heated up to 85 degrees
It doesn't have a 1000lm mode, but it does have a 700lm mode and it will run for about 8 hours and not get very hot