I've seen it done, but it really isn't safe... The problem is that the entire bike's two halves are connected at only two points, the bottom bracket, and the extended head tube. You have to weld the extended head tube on, and weld an extension on the steer tube. I can't think of how you'd avoid that problem. Then the bottom bracket needs to be welded. I've seen even welded BBs break, so we gusset all our bottom brackets for extra strength.

So basically, I don't think it can be done completely weld free, and even if you had the steer tube welded for you, the rest would be highly questionable.

Just find someone who's got a welder who'll teach you. Its really not hard, and it opens a huge set of doors for mutating bikes. Welding is really par for the course. People keep looking for a 'weldless holy grail', but you aren't going to find it, welding is a basic and fundemental metalworking skill.

peace,
sam