UPDATE! Version 2 now available. See below.

Some time ago I uploaded a gantry mounted bed light for the Ender 3 Pro and its variants at https://www.thingiverse.com/thing:6691542. The position of the light behind the gantry aims light under the printhead to make it easy to examine the current layer - very important for that first layer!

I also have an Ender 3 S1, but the frame on it doesn't permit the same mounting method. I really was becoming dependent on the light on the 3 Pro. After giving it some thought, I came up with the idea of mounting the brackets on the 'ears' of the gantry pulley plates.
The mounting brackets are a few millimeters higher than the nozzle, and should never come in contact with the model.

Printing the parts - No supports are required. Print the LED rail flat side down. The inner walls are a 45 degree overhang, and should print without problems. I recommend orienting it at 45 degrees as shown on the build plate so that several layers will be printed longitudinally from one end to the other for optimum strength. The mounting brackets can also be printed without support as shown. PLA, PETG or any other material should work fine.
The version 1 files are still here if you prefer them.

VERSION 2 - (Filenames v30) I tightened up the profile of the mounting brackets and eliminated the part that crossed over the LED, so there is no longer a shadow from the bracket. However, that means that a bit of support is required for a small part. See the Slicer Preview image for print orientation and support. When printed this way, all other angles are greater than 45 degrees. Paint-on supports, if your slicer offers them, will do this nicely.
They should also be a bit sturdier than the previous version.
It still uses the same LED mounting rail, and assembly of that is unchanged.