Original chain will be fine with the 14t. You will probably find that it wares quite quickly. I found the same 'hole' in the gearing when tackling the rougher bits while off road, Others I believe have gone up on the rear sprocket as it in theory causes less strain on the chain.
Wemoto is one supplier to try - there are others.
This link may be help you too.

http://www.xt660.com/showthread.php?...ight=sprockets

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