Hi Onatopp,
according to this:
http://www.strida.com/en/products/?method=listing&sid=3
the correct Strida Part Nr. is ST-CW-001, ST-CW-003 or ST-CW-004 (depending on colour).
ST-CW-001
found here: http://www.addone.tw/tw/products/?method=detail&aid=58
ST-CW-003, ST-CW-004
http://www.rxrmall.com/shop/item/item.php?category_id=5034&item_id=13272
Sadly these belt wheels are sold including cranks, I would prefer something like that :
from here: [url]CNC titanium-coloured front pulley]