Best place is this seller who can be trusted. Recommended for a lot of Soundstream parts.
https://www.ebay.com/sch/originalparts_nos/m.html?_nkw=&_armrs=1&_ipg=&_from=
Send him a message and he'll tell you which exactly are for the Reference 604 unless the photos work for you.
Also, pick yourself up a can of DeoxIt D5 or something similar, NOT WD40. DeoxIt has cans with a Low/Med/Hi flow valve which is nice. Good for pots and switches. All SS switches are a problem, and D5 is a good remedy. Use it on NEW switches too.
https://www.ebay.com/sch/originalparts_nos/m.html?_nkw=&_armrs=1&_ipg=&_from=
Send him a message and he'll tell you which exactly are for the Reference 604 unless the photos work for you.
Also, pick yourself up a can of DeoxIt D5 or something similar, NOT WD40. DeoxIt has cans with a Low/Med/Hi flow valve which is nice. Good for pots and switches. All SS switches are a problem, and D5 is a good remedy. Use it on NEW switches too.