The Xenos is a nice plane; it's a shame it's only flyable by shorter folks
I sat in the Sonex cockpit demonstrator at Sun 'n Fun a few years back, and at 6' 6" I only fit when I sat in the middle of the bench seat with my legs spread-eagled almost to the sides of the cockpit. I'd be building it today if it had been designed with more room inside.
Two other kits out there are the Europa motorglider: Europa Motorglider and the Whisper: Whisper Motorglider. Neither are tandom seating though, and they're both composite kits and fairly expensive. I did try the Europa on for size once at Arlington and, amazingly, I fit just fine. I do love that Europa, but it's a long, expensive build.
This guy has the JT-8T concept plane that looks a lot like what you might be looking for. Beautiful 3D model, but, alas, not real.
I've been following the tandem Ion with interest for some time. It has interchangeable wings like the Europa, and there's been some talk of doing motorglider wings in the future. However, they still have a way to go even to get the Sport Plane kit in production, so I wouldn't expect motorglider wings any time soon.
There are a number of tandem self-launch sailplanes available, but they're not touring motorgliders, and none are available in kit form as far as I know.