I would only use a sauna rated light fixture, ones for this height will have to be a filament bulb, and are often encased in glass. I would also use silicone cabling. LEDs don't handle heat very well, and most sauna ones are only rated for lower levels.

I would use the regular sauna vapour barrier too, and I would run a heat proof silicone cable for a safe distance, rather than a PVC or rubber one.

Here's some ideas: https://www.saunainter.com/en/sauna-lighting/sauna-lamps/?page=2

Also: https://www.saunainter.com/en/sauna-building/electric-sauna-cables/silicone-sheathed-cable-sihf-3x1-5mm--/sk315/ (might be slightly overspecced in terms of thickness for a light)