where to find replacement Waterspring tap washer?

My Waterspring (TM, Denmark) mixer taps need a new washer; my regular experienced plumber can't match the old one exactly, and the temporary replacement is now leaking. The old washer is about 17mm diameter, centre hole 5mm. I have found Waterspring's English language website but can't get in to it. Short of spending on a new mixer tap, what should I do?