I created this mounting plate to replace the all in one 12V USB charger in my RV with a more capable 12V USB QC3.0 charger with voltage meter and on/off button.  This is a simple design that works well and fits  into the original mounting screw holes that were used by the original USB charger ports.  The mounting plates that came with the quick charger were too small and didn't cover the screw holes, so this plate is bigger and covers up the existing screw holes and allows you to use the existing holes to mount the quick charger.

Link to Quick Charger:

https://www.amazon.com/gp/product/B098KD2G8F/ref=ox_sc_saved_image_3?smid=A36QP4GB26KF30&th=1