One word of caution...having the same uke James plays won't make you (or I) sound anything like him. Guys like James, Jake, etc., can wring magic out of a Kala while we mere mortals still sound pretty average even on premium ukes.
Oh...I lied...two words of caution - that video was shot with a very nice microphone in an acoustically perfect space (radio studio).
You're right, it's a G-String James Hill signature uke....and it,s been discontinued by G-String so the only way is trying to get a second hand one.....
It's a custom uke made for him by G-String. They made similar ones as a 'James Hill' signature series as well (http://ukulelefriend.com/?portfolio=custom-james-hill-ukulele-2) but I'm afraid G-String is now closed down so it's not in production anymore. Perhaps if you ask James Hill kindly, he might donate it to you? Or if you're lucky you might find one in secondhand one day.
That James Hill GString was built in 02 by Derek, if I remember right. The signature models were made in 07 (?) and had the slotted headstock rather than the slanted headstock.
I've sent an email to Derek. Being is a nice person he agreed to make a custom uke for me. Not a full replica of James uke, but a close copy. Lalz, He is not out of business. What makes you do such a statement?