I'm not sure about the solderless pipe fitting - I haven't seen one yet. While you may be able to rig something up with PVC, I would only consider this a temporary repair. You should be able to desolder the elbow (heat and pull), clean up the end of the pipes and solder in a new elbow. If it is too difficult to desolder both ends, I would cut at the easier to access end, then desolder at the end near the floor board. You don't want to shorten the pipe that is already close to the floorboard. On the end you cut, you would need to cut back far enough so you'll have room to add a pipe union and a short length of new pipe to bring this out to its original length.