What is an ideal current source in real life?
An 'ideal' current source would have to have infinite voltage range. Likewise, an 'ideal' voltage source would have to have an infinite current range.
In other words, these ideal sources don't exist. We can approximate them by using a power source (like a battery, or a floating power supply) with either current or voltage regulation on its output.
Current sources (and sinks) are nevertheless widely used in electronics. They always have a voltage compliance range limitation that defines how non-ideal they are.