I don't know of a source other than Jaques of London and their's are probably really expensive. I just had a thought that you might be able to find a good backgammon set and use those pieces for checkers. It looks like a backgammon set has enough for an 8 x 8 board but not a 10 x 10 board.
Good Quality Checker Pieces?
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A five second jaunt to amazon, followed by the search query "checker pieces" shows some decent options.
http://www.amazon.com/Chopra-1-75-Wood-Stacking-Checkers/dp/B004IQ5444/ref=pd_sbs_sg_4
http://www.amishhandcraftedheirlooms.com/checkerboardsandchesssets.htm
This site doesn't give diameters, but the large pieces look like what you are looking for.
Does anyone here have a source for good quality checker pieces? 1.75-2" diameter, plastic or wood are fine. Nothing fancy or expensive -- just good quality. I want to add some checkers to my chess kit. Thanks much.