clutch o-rings???

[vs7]

So I was breaking belts...Took apart the clutch--over the course of about an hour I managed to pry off the cover which houses the pins; it was so full of belt debris it would not just slide off. I ruined the o-ring at the top that is supposed to keep the debris out, though I suspect it wasn't doing its job anyway. Does anyone know what size o-ring I should get to replace it? Its a 150cc gy6 scoot.