Alan,
I assumed M&P would also have the left points but it looks like they may not. They certainly have the correct condensers, see KZ650 parts.
12months ago, I had a choice of at least 6 suppliers in the UK for points but they are not coming up on Google. Found a set in the US for about £30 inc postage but you may wish to keep searching in the UK.
Few tips for the pistons, warm the pistons with a heat gun before pushing the piston (gudgeon) pins in or out. Be careful to line up the ends of the rings with the locating pin in the ring groove before sliding the barrel down. Ease the rings in with your fingers as the barrel comes down. Coat the cylinder studs with copaslip, ACF 50 or Corrosion Block before fitting the barrels,they have a habit of rusting. Ensure the L/R cylinders and heads do not touch each other when fitted or you will end up with a mystery tapping sound when the engine is running.
Brian.