Anything original that's be lying around won't be much good now. It may be possible to get some mixed & put in a spray can - contact a local body shop: they might be prepared to it, depending on what supplier they use. If you know the paint code (I'm only au fait with Fastbacks) then I could try my local chap if you don't have any luck. Cheers. G.
Get in touch with Turner Trade Paints in Cannock. They specialize in classic car paints and do a full range of celulose based paints just for that purpose. They do very good quality aersols for about six quid. Unfortuantely their website is quite rubbish and hasn't been updated for a good few years. Linky!