I couldn't find anything good on-line, so I soldered these up using readily available parts.

Schematic

Hello and good day MarkusXL. Thank you for sharing this accessory you have created for your DJI Robomaster S1 and thank you for your valued support. Please stay safe always and keep on driving.

MarkusXL Posted at 8-7 11:45
Schematic

And you connect straight to the PWM port?

Do you use power & ground (always on) or signal & ground (controlled through PWM)?

gpvillamil Posted at 8-9 14:34
And you connect straight to the PWM port?

Do you use power & ground (always on) or signal & ground (controlled through PWM)?

Oh its working pretty well - if you plug it in one way, it's full brightness on all the time, no software control.

Plug it in the other way, PWM = 0% =  90% or better of full brightness, down to 100% = Off with software control.  Yeah, it's counter intuitive.  But to get close to 4.9 Volts you need 0% duty cycle.  At 100% duty cycle your RMS voltage is close to zero.  Plug it in the other way to get a solid 5.1V on all the time.

Sadly, the default PWM is 0% so the default for these simple lights is always on, but you can code them to flicker or flash or fade as you like.

At full brightness, they represent a measurable battery drain at almost 330mA at full 5.1V input.  That current was also too much for those 1/4 watt resistors so I upped them to a 1/2 watt.  They still get a bit warm.  Wasted power but this is a cheap and simple circuit.

When I get time I will wire my cheapo o-scope so we can all see the diff between 0%, 50%, 100%

MarkusXL Posted at 8-9 14:50
Oh its working pretty well - if you plug it in one way, it's full brightness on all the time, no software control.

Plug it in the other way, PWM = 0% =  90% or better of full brightness, down to 100% = Off with software control.  Yeah, it's counter intuitive.  But to get close to 4.9 Volts you need 0% duty cycle.  At 100% duty cycle your RMS voltage is close to zero.  Plug it in the other way to get a solid 5.1V on all the time.

Yeah I figured it's switched ground, so PWM 0 is full bright. It's a shame, it would be nice if a custom action turned the lights on and then switched off when you stop. Maybe add little CMOS inverter in there. This part is $0.36 and should do the trick:
https://www.mouser.com/datasheet/2/308/MC74VHC1G14-D-110624.pdf

Lol the headlight saga continues!  I found a much better solution, maybe even worthy of adding that inverter.

With purchase Harbor Freight gives away these flashlights with an incredibly bright LED strip that looks perfect for the job, and draw less battery power.

Back to the soldering bench...

Finally, I got adequate illumination from this setup.  Still at around 330mA battery drain but much brighter than before, now that I am using a light strip taken from cheap flashlight.

Also imaged, my cheap scope is reading the PWM port - you can see the diff between 50% and 75%.  Great for dimming the headlights if you don't mind some flicker.

That's awesome.