I've found recently that CR18s are sometimes thin on the ground depending upon drilling. 36 hole are the most prevalent recently, but how many of us have bikes with 36/36 or 36/40 holes front/rear? Most of the British 3 speeds are 32/40. Might be best to slip the service managers of various LBSs a fiver or a 6-pack just for a weekly heads up on CR18 availability. Worst case scenario, you find a 32 hole and build up the wheel that has the most brake power.
With my recent ROH build (track bike) I searched for weeks to find an appropriate looking pair of rims in 700c with 32 front, 40 rear drillings. The 40 hole rims came from
WGB here on BF.