Hi Winfried,
Me too, don’t like to carry backpacks on my back so I’ve ordererd this rack http://www.fahrrad.de/fahrradzubehoer/fahrradtaschen/klickfix-vario-rack-schwarz/253987.html
It can be installed on a head tube of your Strida via a klickfix adapter like this: http://www.klickfix.de/index.php?mod=17&kat[c]=-1&lang=en
Here are pics of this done by a member of this forum 
flickr.com/photos/genuine_st … hotostream