Piece of a large log (Twickenham TW2)

Hello everyone. I'm looking for a piece of a large-ish log to use as a surface to cut wood on. It will have to be a piece of a log about 15-20 cm long (if laid on it's side), cut flat on both ends with a diameter about 30 to 40 cm. If you have anything you think might be suitable, please let me know. Thanks!