The main fibre washer that has to be replaced, is the one that goes under the carby bowl retaining screw. It often doesn't survive being disturbed, when the bowl is pulled off. The others are also usually fine unless dismantled.
Fibre washer assortments are available in places like Bunnings plumbing section [~$4.50 for a 30 pk], and there should be something suitable as is, or usable with a bit of file work on the ID, in those.
Just a tip: to help the new washer survive a bit better, smear both sides with grease/vaseline before installing it.
