(I know this wasn't the point of the original post, but it throws up an interesting discussion...) Someone, somewhere in the paddock will have the bits you need, and I'm sure they'll be willing to lend them to you...
...just make sure you give them back or replace them once you're done!
It probably makes sense to have simple things like bars and maybe cheap replacement brake levers, footpegs and enough tape, cable ties and fasteners to replace damaged fairing!
I always went on the premise that if I did something big enough to damage the bike in a major way (lost a wheel / bent a fork / etc) then I'd probably not be in a fit state to ride the next race anyway
