Box makes a good point (I have a spare rear wing, slightly scratched, but there's not enough room for it, me and clothes). That said I might have some small bits kicking around, so I'll bring those.
FYI; I remember on club outings in the UK we would coordinate certain spares in case anyone had a problem - again small stuff (throttle and clutch cables, that kind of thing), but with the range of marques/engines etc. that might not make sense...