Bestblatt.com has the new decoded batteries (price $22.75):
“New Li-Ion ID-Security Rechargeable Replacement Battery. This battery is fully-decoded and 100% compatible with most current firmware version v1.1, v1.2 or later. Works wonderfully for:
Panasonic DMC-G1, DMCG1
Panasonic DMC-GF1, DMCGF1
Panasonic DMC-GH1, DMCGH1
Panasonic DMC-G1K, DMCG1K
Panasonic DMC-G1R, DMCG1R
Panasonic DMC-G1A, DMCG1A
Panasonic DMC-GF1C-K, DMCGF1CK
Panasonic DMC-GF1K-K, DMCGK1CK
Panasonic DMC-GH1K, DMCGH1K
Panasonic DMC-GH1W, DMCGH1W
Panasonic DMC-G1KEB-A
Panasonic DMC-G1KEB-K
Panasonic DMC-G1KEB-R
Panasonic DMC-G1KEG-A
Panasonic DMC-G1KEG-K
Panasonic DMC-G1KEG-R
Panasonic DMC-G1WEG-A
Panasonic DMC-G1WEG-K
Panasonic DMC-G1WEG-R
and more models.”
Thanks Jerry for the link!