Hi 13down, I've been looking for one as well and have been refreshing theukulelesite.com at least 50 times a day religiously to see if they have any new ones in stock. This one literally just popped up a couple hours ago:
If you're looking for one of the other models I think those will be available soon, I spoke with Corey over the phone in December and he said they will get a major Pono shipment in March so I am thinking any day now.
I'm part owner in Dixie Ukuleles and we are a Pono Dealer. In their 2014 catalog they listed under "Pono Thinbody Electric" was a thin body baritone with a retail of $729 and a deluxe thinbody baritone at $879 both have passive pickups with Mi-Si pickups at an additional charge. At Dixie we have not carried the Thinbody Electric models. If you really want one call any Pono dealer and he can contact the manufacturer to see if any are in stock.