First time I've seen a Pico Squeeze. If that tank has a larger capacity than 2ml, which is likely gauging from the image, then you won't be able to legally acquire a replacement tank that size. 2ml tanks are fine but for having to top them up more often than a 5 or 10ml one. It's easy to buy a regular Pico on the High Street and a vast range of different tanks to screw on to it.