Citroen C4 Picasso, How To Change The Key Fob battery. - YouTube
Citroen Grand Picasso Replacement Battery for Key Fob / Remote (2 Batteries) | eBay
Jongo Key case without blade, compatible with Citroen C4 Picasso, C4 Grand Picasso, C5, CE0536, with 1 x Maxell CR1620 battery, 3 key case for car keys : Amazon.nl: Electronics & Photo