Stereo Exchange less-likely will be willing to sell a part. They worry too much about their wallet thickness.
Meanwhile I'd check input transistors of that faulty module one-by one and it's not too many maybe 2 or 4 depending on circuit design. Sometimes inspecting under the loupe will give you some visual on cracks, burns and part codes that not visible anymore compared to 'healthy' transistors.
There's plenty of info on how to check transistors operational condition, but I'd usually check for short(continuity between terminals) first, than do the diode one-way conductivity check.
Meanwhile I'd check input transistors of that faulty module one-by one and it's not too many maybe 2 or 4 depending on circuit design. Sometimes inspecting under the loupe will give you some visual on cracks, burns and part codes that not visible anymore compared to 'healthy' transistors.
There's plenty of info on how to check transistors operational condition, but I'd usually check for short(continuity between terminals) first, than do the diode one-way conductivity check.