This bracket will allow insertion of rectangular rocker switches and has an opening of 20mm X 12.5mm.
Orient with the large opening on the build plate and most printers can print without any supports. The only overhangs will be the 2 screw holes and if it isn't perfect, it doesn't really matter since you're going to run a screw through it anyway.
Parametric file is shared with my OnShape account at:
The switches I used were from this link:
https://www.amazon.com/dp/B082PQQ8K3?ref=ppx_yo2ov_dt_b_product_details&th=1
The author marked this model as their own original creation.