There are a couple of Sunn Sorado Bass amps for sale on eBay. They are the same thing as the 200 S with exactly the same schematics - tubes and all. Both have the KT88's and are 60W RMS into 8 ohms.
Back in the day Sunn used the same chassis but gave it a different name depending on the speaker configuration, and the year it was produced. If you look up the schematics on line and compare them, you will see that the two are the same. For instance, I have a 1967 Sentura II with no mid-boost switch. In 1968 they added a mid-boost switch and the 1968 Sentura II and the 1968/69 Sceptre are exactly the same amp. The difference is that the Sentura II came with a 2x15 cab, and I believe that the Sceptre had the tall 4x12, (not the Marshall style 4x12)
If you can't find a 200 S maybe one of the other bass amps would do.
Rob
