As of today, Amazon can only deliver the set. Individual batteries can be found currently only about finding of MarketPlace retailers.
UPDATE 19.04.2013:
Here there is the 4-pack of the new version (2nd generation "B"):
Sanyo eneloop HR-3UWXB-4BP AA Mignon battery (2450mAh, 4-pack Original)
Difference between 1st and 2nd generation:
+ 2450 instead of 2400 mAh (This is the "minimum specification", the 1st generation had are "typical" capacity of 2,500 mAh on the packing!)
+ 15% discharge after one year instead of 25%
UPDATE 10/10/2013:
Not yet available in Germany, but after Panasonic has taken over the brand Eneloop, there is now the 3rd generation in Japan under the name "Panasonic eneloop pro" and the model name "BK-3HCC". I think the end of the year there is also with us.
Difference between 2nd and 3rd generation:
+ 10% discharge after one year
Otherwise no changes.