Semi-permanent USB power supply?

Hi all.

So I have an Amazon Echo in my car, which sits in a 3D printed holder that goes into the cup holder right in front of the 12V socket. In the 12V socket, I have a USB phone charger adaptor that supplies the Echo. The audio is connected via a lead to the AUX socket in the same area. All the excess lengths of cables are hiddin in the cup holder underneath the Echo. It all works very well...

...apart from the fact that the connection between the USB charger and the 12V socket cuts out every time I go over a bump or move my phone if it's connected. I've tried multiple chargers, but they all exhibit the same problem. I've checked the connections to the 12V socket and they're fine. It's just the nature of the beast. I had the same issue with completely different hardware in my previous car.

The rear 12V socket is in use by the kids in the back and would probably have the same issue, so I can't use that.

What I want to do is in some way have a semi-permanent 5V supply for the Echo. I already have a dashcam semi-permanently connected via an Add-A-Fuse adaptor. So I could maybe route a new 12V supply to the area from the fuse box, but that seems like a hassle when there's 12V already there. Or I could simply make a spur off the 12V supply already available underneath the 12V socket (or the rear one).

Then there's the question of how to drop the 12V to 5V for the Echo. I've got a ton of buck converters which I could use for the job which would be small - happy to do that. Or I could buy a ready-made 12V USB adaptor, like the one I already have, and hard-wire it (i.e. solder the damn cables onto it) so the connections are always good.

Which brings me to my final question... how do I do this without having loads of wires everywhere? If I hide the wires/electronics in the area underneath the 12V socket, is there a good way to get the 5V USB cable out to the Echo? Is there space under there?

Alternatively, there's the car's USB port. It's in use, but I could get a small USB hub to split it off. But I can't find any specs in the manual that state how much power it can supply. Does anybody know for certain?

Any thoughts/ideas? In short I just want to get a reliable, ignition-switched, 5V supply to an Amazon Echo where the central cup-holder is next to the driver.

 

That's a good idea! I'll try wedging it!