I see; first we have here a small communication issue, but at least that can be solved easily 
Please download this pdf
Strida 1 manual
and take a closer look at the last two pages.
Most likely youâre searching for part 14. âFront pulley mountingâ ?
(Iâd call that simply beltwheelâŚ)
This part can be found for Strida 3 versions - not sure whether it will fit a Strida MK1âŚ
http://strida.fr/pedales-pedaliers/53-pedalier.html