where can i get an exhaust stud for a polini 70cc kit?

my exhaust stud is a bit messed up so i need a new one....is it possible to get the same stud for my kit?

 

dont you have one from the 50 barrel that the 70 replaced?

 

yh i tried it but it seemed a bit bigger and started to thread the whole so i took it out. I might of put it in a bit wonky coz i was in a rush but ill try properly tomorro.