Race bike restoration

 
Hi guys
I bought a 125 bantam race bike about a year ago and have just started to restore it . The guy I bought it from tould me it was built by a fella called geoff pitcher and raced in the 1974 TT.
I have rebuilt the bottom end but am struggling to find a race piston .
The piston that in now looks like it was a single ring and has had a dykes type ring fitted above . Inside it's marked BSA 90/1564 on top +40 and measures at 52.75 mm .The skirt on the inlet has been trimmed and the inside shaved out to accept the two stuffers. 
 
Can anyone help or know where I can get a 53.5 mm piston to suit ?
Any info on the bike so I can restore it to its original race colours etc would be great!
Dose anyone know geoff or his race mates from the 70s that may be able to help ?
Thanks
Mac

Go to the site memberlist , Geoff is there somewhere and you can click and find his PM address and can contact him. Derek Betts can maybe supply a new piston, contact him the same way .
Welcome to the Bantam fraternity .

Trevor

Thanks
I will pm them,hope they can help bring it back to its former glory
Regards
Mac