Wondering what other rear shocks fit CB1 for 2nd hand cheap replacement, have seen other people say cbr900 shock fits ? if so which year ? any others ?

Some CBR shocks fit, but the spring rate is all to cock, so it is not an ideal replacement. You would need to fit your original spring back on. I do have a 180kg 7" spring, that might fit to sort the spring rate out, but you'll need to compress the spring to swap them.
I don't think a definite compatible replacement was ever found.