I have made grips from the 'bark mulch' products sold at lawn centers. Similar to this.. http://www.homedepot.com/p/Gardentim...0160/100336461 A $5 bag is enough for many, many grips.
In size 'large'the chips are about as big as your fist and I can get several hole saw cores out of each one. I start with the hole saw mounted in my drill press. I drill half way from on side then flip over and drill the rest from the back side, this leaves a cylindar that sticks out from the saw enough to be remove with you fingers, no prying.
I then place the cores one by one in a simple jig (whole drilled in a block of wood) and sand one side flat and flush to the top of the wood. A second jig slightly shorter is used to sand the reverse side. This squares up both ends, makes them all the same sze and shape and provides for a clean, flat glueing surface.
Now you have a bunch of disks that look very much like commercial cork rings and can be assembled in the same manner.