If you're looking for that NOS Kashimax seat, but your wallet is objecting, this might be the solution.  This is a late 70s/early 80s Apex brand BMX saddle, which is very similar to a Kashimax.  The material is quite hard, but besides the scratches (visible in the pics), it is straight, solid and in very good condition.  I'm sure you could probably sand out the scratches, but as is, it's a nice survivor specimen from the golden age of BMX, perfect for your SE, Hutch, GT, Robinson, Mongoose or Kuwahara build.