I'd guess that even if this the same Sanyo Denki they just made the part as subcontractors to Stax and either won't have stock or won't deal with the end user.
http/www.sanyodenki.co.jp/en/
Stax are still in business but note that they are not accepting emails from the public and instead direct you to international distributor list.
http/www.stax.co.jp/