Home made extension for the Canon Remote release.
Cut the Canon cord to expose 3 wires.
Attach male and female stereo mini-plugs (#1 and #2)
matching the 3 wires.
Make an extension cable with the same plugs on each end.

In this case, I already had a 10' stereo extension cord (#3)
with molded plugs (Radio Shack) that I had been using for another
application. Therefore, my only expense was the 2 plugs used to
splice the remote's cord.
Cost only about two dollars, compared to $75 or more to
purchase the official Canon extension. No need to purchase
plugs to match Canon's plug and camera socket.