Here are some instructions for anyone in a similar situation. All you need are the common things most cyclists have, or bike shops should give out for free.
You'll need an old SRAM chain box, the chains are sold inside these plastic boxes. If you don't have one lying around, then a friendly bike shop should let you have one from the waste box. You'll also need some electrical tape, three small zip-ties and a small sharp screw driver or pointy-ended thing to make holes. An elastic band is an optional extra.
first up, a couple of pieces of electrical tape on the stem to protect the paint and prevent vibration/noise.
next place the base of the box on the stem, and line up where you want the holder to site, marking where you'll make the holes for the zip-ties. Use your small screw driver (or pointy-ended thing) to puncture holes in the base of the box. The plastic box is soft-ish (not hard like a CD case) so it won't shatter. Once you're done, zip-tie the base in place.
although this is not a waterproof route card holder, you can improve the basic resistance to rain with some electrical tape over the zip-tie holes. In preparation for a downpour I'd recommend just wrapping the route cards in a sandwich bag, inside the holder.
and that's pretty much it. Put the route cards inside, and go. About a quartered A4 sheet fits, or a slightly trimmed blank postcard size. The optional elastic band can be fitted through the shop display tag for additional lid security.
and on the road, the elastic band helps with food storage...
hope that helps,
cheers,
