While I don't agree with the idea, here is a way to do it.

The easiest rudder to retrofit will be a SmartTrack system by Cascade
Designs

http://www.seallinegear.com/smarttrack.asp

To run the cables and mount the bracket, you will probably have to
grind out, then re-install the rear floatation chamber on your Magic.
Other than that, it is a very simple bolt-on application.

The SmartTrack rudder is not a full flip up rudder like on some sea
kayaks. It flips 180, not 270, so it sticks straight up in the air. On
the canoe, it will stick up out of the way without bashing, jamming,
or jackknifing against your hull (which is why I suggest it over other
rudders).

Toe Pilot Foot Controls (footbraces) $99.95
Rear Mount Blade Housing $104.95
Rear Mounting Bracket $19.95
Foil Blade (single) $24.95 (tandem) $29.95
Cable Tubing Kit $24.95

You are looking at $274.95 for the parts.

There are cheaper systems avaliable. Seda www.sedakayak.com will sell
a Feathercraft retrofit (fits Seda kayaks, and can be modified to fit
a canoe) for $195. You can also take the SmartTrack system and switch
the Toe Pilots with Yakima ($34), but the Toe Pilots are worth it,
they are good.

Personally I would go the SmartTrack route, because it will be the
cleanest looking installation. Just about any rudder kit can be made
to fit.

- Eric