The great thing about the following bits is that it also solved the issue of relocating the ignition as I'd also put some fat bars on the bike.
DRZ400 Ignition key and USB mounting bracket - $58
https://www.facebook.com/marketplace/item/2670086546420290
Initially I was considering buying a MOTOdash MD4.1 but it's plastic construction and the fact it had to come from the states kinda put me off... It looks like a neat bit of kit but I wasn't convinced it would stand up to the abuse of offroad riding. With shipping from the USA to Australia it came in at $64 which wasn't bad, but it could end up being a pricey mistake...
Then I found a 3D printable version online which looked good but after some investigation, I found it was going to be $100 to print in tough enough plastic and again, I had no idea how accurate the 3D model was.
Eventually, I found the solution on a random search in Facebook Marketplace. Warren Fincham makes these himself and it looked spot on! Clearly a lot of R&D has gone into the design I really liked the idea of supporting a 'garage enterprize' so after a quick chat with him, I purchased a unit at $58 inc postage.
He's even knocked up a video on how to install it:
USB charging socket - $16
The next challenge was finding a USB charger socket. Nearly all the units I found on eBay either had two USB sockets or no way of turning off the unit other than disconnecting it from the battery. After a lot of searching I eventually found the perfect item: 1 USB socket, an on/off switch and a bonus volt meter (which turns out to be supprizingly acurate!).
The only downer with the unit was that the orientation doesn't match the photographs which means the volt meter is at a 90 degree angle... Not a deal breaker though.
Phone mount - $17
This actually turned out to be the trickiest item to source... I'm not a big fan of the X-Grip style of mount as the 4 prongs seem to come into contact with the volume and/or power buttons on most phones. The Quad Lock system is probably the most solid solution which doesn't interfere with the phone buttons but it's expensive and you have to get a case that matches your phone...
Baring in mind that the phone I use on the bike is a Samsung Galaxy S6 I picked up on Gumtree for $40, dropping $100+ on a mount seemed a little excessive...
So I trawled the eBay listings for hours looking for an alternative and after 2 failed attempts (the 1st one had a really long stem so the phone stuck up higher than the bars, the 2nd one a crappy mounting kit that didn't work with the fat bars) I finally got one that was perfect.
The nice thing about the mount is the short stem so the phone sits nicely between the bar risers, it's small and it doesn't mess with the phone buttons. You can also have the phone landscape or portrait. I have mine set up in portrait mode as it means the phone doesn't bash the petrol tank.
RAM Mount Tether $6
This item wasn't part of the original plan but during my research I'd seen a lot of bikers use this with the X-Grip mounts. It works perfectly with the phone mount and at $6 it's a very cheap bit of insurance against the phone bouncing off into the bush if the phone mount screw loosens off.
Short 90 degree usb cable $1.50
I found that a standard usb cable stuck out to much but this one sits flush to the dash and the base of the phone without loads of cable dangling around.
Putting the whole thing together took a couple of hours as I had to remove the seat, plastics and petrol tank to run the power cable from behind the front headlamp cowl back to the battery. I used an inline fuze that I cannibalised from another USB/Cigarette lighter socket I had kicking around as I figured a little extra protection to stop anything nasty frying the electitrics couldn't halm. With all cables and terminals wrapped in electrical tape and the bike put back together I was good to go - and it works a treat!
The final piece of the puzzle was getting an app that locked the phone in landscape mode. Android seems to support locking in portrait but landscape is triggered by rotating the phone and I found that the screen would sometimes rotate when going round corners... So I downloaded the Rotation Control app from Google Play and that solves the issue. It has the added benefit of rotating the home screen too which makes navigating the apps etc on the phone loads easier.