The Mahle parts seem to come up on ebay from time to time, try there? They may no longer be in production as they seem to be less common. But there is a lot of old stock out there, all around the globe, for these engines thanks to the millions that were produced over the decades. So even after end of production, NOS parts seem to be quite prevalent.
I don't really think you can go wrong with KS pistons though, if you have a source for those. I know Tom is not partial to them because he has found that they tend to be slightly "short" (distance from wristpin to piston crown less than factory) and thus the piston protrusion out of the block deck is less and headgasket selection options become more limited. But I believe the reason KS pistons are built this way may be that they assume if you are installing oversized pistons, you likely will have also had the block surface milled. If that is the case then some material will have been removed and that will partially compensate for the shorter pistons, which may be shorter by intentional design for that purpose. You could even decide how much block material to take off based on your piston measurements (comparing what is removed from the engine vs the intended replacement parts) if you wished to control it directly. So in short, it's a solvable problem, if it's a problem at all.
I don't know what Parts Place stocks but they are a longtime reputable retailer. I am sure you could call them and ask.
