you can get it from Grizzly Service centre UK tel 08707876177, but it costs £41.78, so you may as well chuck it out and buy a new machine.
My battery went flat after only one summer season, and they say the 3 year warranty doesn't cover batteries. So I'm very annoyed and will avoid LIDL cordless tools from now on.
Useless_Lidl_tools, May 2013