I have seen some wrap that is supposed to work, I haven't use it and am frankly skeptical.
If the leak at the elbow is due to a poor solder joint, it will be easy to fix, but the water has to be turned off and the pipes completely drained. It is for repairs like this that I learned to solder copper pipe and have a torch, flux, and solder in my shop. Since you don't have the tools/know-how to fix it yourself, you could try that tape from HD or Lowe's type stores. Or, just get a big garbage can and catch the drip.