How about a friction folder? If you can deal with no lock,I would suggest contacting one of the makers in the exchange.
Nice recommendation. Even without being locking, it seems like the design makes it so that as long as you're gripping the handle, it's unlikely that the blade would move. It also seems that opening them one handed isn't that difficult.
After looking around a little, I came upon Michael Morris' friction folders. I sent him an e-mail detailing what I'm looking for within the bounds of what he offers in friction folders. We'll see where this goes!