To all those trying to utilise foil, mirrors, CD’s etc I don’t think you will have much luck. The problem is not that they are not reflective. It’s that they are too reflective in one direction only.
If you take a CD and shine a flashlight at it, the result will probably be a fairly tightly focused spot of light on the ceiling or wall somewhere. Now imagine that flashlight is your IR array and your wiimote is right beside it. It suddenly becomes quite obvious that all your IR is being bounced away rather than reflected back. Your CD/piece of foil/mirror is going to have to be at a very specific angle to reflect that light directly back to the Wiimote. Something that’s not going to happen if you’ve got little bits of it on your fingertips and they are moving all over the place.
The material that Johnny uses, And the material that the previous poster suggested getting from a bike shop (Aaso the reflective saftety tape you can buy to stick onto kids clothing )all do the same thing. Their surface is multifaceted so that whatever direction you shine a light onto it from, it will be reflected back to that light source.
I agree with Karma, buy some tape and ditch the mirrors