How to deal with non-working key on the keyboard?

I've problem with my Macbook Pro (with El Captain installed on it) where one of the keys (such as r) doesn't work at all, so each time when I'm typing a word with "r", I've to keep pasting it from the system clipboard. It's very inconvenient.

I'm planning to see Genius Bar, but since then, I'd like to find a better way to deal with such problem.

I've also consider external keyboard, but it's another inconvenience, where you have to carry it physically with you.

Is there any way of rebinding a keyboard key into another one (like r into §)? Or do can you suggest something better?

As suggested in the comments and in this post, using Karabiner app should work with the following configuration of private.xml file (edit in Misc tab):

<?xml version="1.0"?>
<root>
  <item>
    <name>Use § to type R</name>
    <identifier>private.replace_r_key</identifier>
    <autogen>__KeyToKey__ KeyCode::DANISH_DOLLAR, KeyCode::R</autogen>
  </item>
</root>

and enable newly created item after reloading the file in Change Key tab.

To find out the right key code, use EventViewer in Misc tab.