I don't know where to find the spare wheel. A wheel got rotten and I want to exchange it.
This is an older, discontinued model so finding a spare wheel will be super difficult to impossible. You can always try to contact the manufacturer, Bébé Confort through this customer service contact form, but they won't have these with most probability. My course of action would be to go through classifieds and try to find a cheap used High Trek pram to buy for parts - and use whatever you need.