Not to my car, but to the wife's, and fitted this:
https://uk.banggood.com/DC-DC-7-28V-to-5V-3A-Step-Down-Power-Supply-Module-Buck-Converter-Replace-LM2596-p-1536688.html?rmmds=myorder&cur_warehouse=CN
to replace a 5V USB output to her dashcam. The old module failed and instead of pulling out the USB lead which had been neatly tucked up the A pillar and across the headlining, I thought I'd just fit one of these. I like it because it has a potentiometer to adjust the output. Quite happy with it and the size is a bonus!