Does anyone know where I can buy rubber hoods for old school Shimano 600 brake levers? The ones pictured
These are a bit of a pain I'm afraid - Nobody makes repros, so your 3 options are
Look out on ebay/forum classifieds etc for hoods or a complete pair of levers
Use the best fit - in this case I think it's Dia Compe (e.g. here) - can't confirm which other ones will work as vintage Shimano's not my specialist subject
Use the damaged ones you have to make a mould and then cook your own - not sure how this is done, but there's a guy in the US that makes Campag record & Universal hoods as a cottage industry.
These are a bit of a pain I'm afraid - Nobody makes repros, so your 3 options are