From the viewpoint of a symbian devotee, the link below gives kudos to a supplier of quality 808 replacement batteries who also does a bl5j that might be worth a try:
http://www.allaboutsymbian.com/flow/..._Nokia_808.php
Not tried them myself, but will advise if I go that route....
Having just had another look, I do not see any more of:
http://www.ebay.co.uk/itm/2x-Battery...item56673afce7