I thought some here might like to make a mental note of Patrice of Clinique Audio in France. I needed a power switch for my Yamaha M-4 power amp and a rec/play switch for a K-950 cassette (both 1979-80). It turns out that Patrice had both in stock. He has been servicing vintage Yamaha kit for decades and has a serious hoard of parts. His prices are extremely reasonable and I recommend him to you. I'm loath to publish his phone number here but he can be contacted via pm using the AK link above.