Will preface this with: You will have more control and better ability to travel upwind on a quadline kite.
That said, larger dual line kites would include:
Peter Lynn Peel - out of production, but available in sizes up to 10M. May be
available used.
HQ Capricorn 5.5 - also out of production, may be available used.
Sieger's Vliegers NPW5: available in 4.85m, 7.00m and possibly larger sizes as a custom order. May be flown on 2 or 4 lines.
If you are riding on asphalt or concrete, a skateboard might do fine. Houston Airhead has done this:
If there are a lot of road irregularities, you might do better on something like an MBS Carveboard which has pneumatic tires. If you are trying to ride on grass or dirt, a full-on mountainboard might be a better choice.
ATB,
Sam
"I never had any friends later on like the ones I had when I was 12 - Jesus, does anyone?" - The Body by Stephen King
A four line kite is actually easier to launch and land and really not any different to fly. You usually just use the brakes a little to speed up a
turn or to land the kite. 4 line powerkites don't fly backwards (usually!) like a 4 line stunt kite will do (Revolutions etc). And you wind all four
lines up together (or stuff 'em) so it's no different there. Plus you can put your brake lines around a stake to keep the kite parked on the ground
when you land. And if you crash the kite upside down, a quick pull on the brakes gets it going again. Much more control, very little difference in
flying them and much safer too. (pull hard on both brake lines and your kite stalls and falls to the ground).
4 line is not a lot more complicated but a whole lot more useful. + Can still be flown on a bar if that is what you are after.
Pretty much any foil kite will fly as 2 line ? ( some better than others ) You just have to tie off or remove the brake lines. This was a very popular
thing to do with older Blade kites for water.