I'm trying to run a fork with a steerer tube that seems to be a little under 1-1/8". I've got a Cane Creek headset, and the product literature suggests inserting a spacer under the headset top cap. It makes perfect sense, after reading it - with a narrower headset, the compression ring sits lower against the upper headset bearing.

Anyway, where can I get a spacer of the appropriate thickness (<1 mm)? Is that something the LBS would have handy?