I only know this page to buy gasket kits for this cylinder, but it is a complete gaskt/jointkit, not only the headgasket and it is expensive
http://www.goetz-motorsport.de/go/goetz ... Xxqpw7V5A$)/s,showModuleObject,9_q1klWYtB,cxW0_xm1oxa1_xm1dtqZgVG,4Fa0jtW3hxW2nB,8xa0nVX0_JH,nRXYoxF1m_a2uAb1jRW28Rr1uMTNn1TNlAD,nB,9VG,hxGZplWZnxC1mxGZpNG2nxmY6RXZbxa1dVq1jQXZ86a0dhqLhxG2jJH2__G0_xCZdNG-oVb0bVa0jcX3g_a09Va19_qYcRr16Rb3.html
^^ This one of the is the biggest shops for Motorbike Equipment in Germany and I am sure that they also sell articles to france.
I only offer complete 170cc Cylinder Kits (with gaskets) for 379 Euro, but no single gaskets / joints.
Edit: Sorry I can´t post the direct link, just use the above mentioned link and fill in the search (white field) the number
3537510Gasket kit = Dichtungssatz in germany