Target & Big W have a Playskool branded balance bike that can have pedals added.
They also have a wooden Thomas the tank engine one (without pedal option).
The one I have is a JDBug one (can purchase pedal kit) I got from an eBay store (brand new). They sell them all the time.
And yes, I can confirm, they are huuuge in Germany and have been for quite a few years.
It is hard to say from what age they are suitable. It depends on your child's motor development. Some kids are fine on them at 2 (although they might take a little longer to get the hang of the balancing thing), others are more ready for it by the age of 3 or 4. I think 2 1/2 is a good age to get them but as I said, some kids are ready for them earlier.