I've done so on the CLB-2 by pulling the pads out of a cheap YSB "X" pattern brake blocks. I dremeled the V-shaped groove on the YSB's just a bit narrower and rounded one edge. They fit the CLB holders very well after that.

Most of the cheap, generic pads on the market should be adaptable in the same fashion, and since the CLB-1 is self-energizing, the quality of the rubber isn't particularly important - in fact, good compounds such as Kool-Stops may be too grabby and cause damage to the brake as a result.

-Kurt