Thankyou for the reply pitpop.
I will be looking for an orion alpha 5 port piston and sleeve set on my next parts purchase.

I was taking the back plate off to perform after run maintenance but unfortunately I had forgotten to make sure the piston was near tdc and unfortunately when I forcefully pulled off the back plate, I tore the longer edge of the piston off because the bottom of it had been in the groove of the back plate. The piston top surface has not been damaged but is missing its "Skirt" if you can understand that???

Thanks again.
Brendan