Hello vreis,
there are several posts about the part already at the forum:
[url]MK1 top plastic socket broken - #10 by Amuro_Lee] 
http://www.stridaforum.com/forum/viewtopic.php?f=5&t=3338&start=0&st=0&sk=t&sd=a
http://www.stridaforum.com/forum/viewtopic.php?f=5&t=3409&start=0&st=0&sk=t&sd=a
http://www.stridaforum.com/forum/viewtopic.php?f=4&t=3215&start=0&st=0&sk=t&sd=a
You might also use the forum search function (upper right corner) and try “MK1” or “Strida 1”. 