Thank you. Could you provide me with a link to an appropriate valve extension. I can't find one that fits in amazon. I suppose I need a tube thing that is 1 foot long?
My problem is solved. I found out that a spacesaver for a Toyota Avensis (European model) fits like a glove, as a wheel and in the trunk. The dutch equivalent of e-bay provided me with a second hand spacesaver spare tire. For €45,- (~38 dollar) I found an unused space saver sparetire 125-70-17". Thank you all for the help!