I buy all of my reeds and lanyards (and some wood) from HUT products. They are specialists in the call department. I do see now that CSUSA carries these things as well, and it looks just like the HUT stuff so it is probably supplied by them.
I don't buy the predrilled wood, but if you dont have a 3/4" and 1/2" drill bits you might consider it. The adapter for the mandrel is made up of rubber bushings that slide down the mandrel and uses the same nut. When you slide your wood over the bushings and tighten the nut, it compresses the rubber and fastens the wood to the mandrel. Simple but effective.
The instructions come with the mandrel adapter kit. You can be as creative as you like with these and they sell quite well. I only have one left in my stock from about 35. The reeds are pretuned, so you don't have to know how to use them to make them (thank goodness!!)