I used an old GEPE cold panel, and went it started to go bad I got a LED panel from Amazon
Light was in "lines" so I put some drafting paper on top of it and separated the neg from the light about 3cm and it worked fine
I guess a small piece of white or frosty plexiglass would work better
I also designed a carrier for my camera on the enlarger column to maintain the parallelism between sensor and negative (based on the old Nikon copy stands)
It is customized for my camera and enlarger but can be easily adapted for any camera.
Repro-Copy Adapter for Pentax