I had several LJ12A3-4-Z/BY induction probes, but unfortunately the size is a mismatch with Prusa's excellent new extruder for the MK2. This converter can be bolted onto the usual induction probe holder to allow the use of 12mm probes. With some work, it should be easy to convert it to also use 18mm probes.
Simply use a piece of 8mm threaded rod or such to keep in place.
Prusa i3 MK2
Easy to print. As you can see from my images, no issues resulted from a small misprint from one of the thinner areas.
In Marlin, the options for this holder are:
X_PROBE_OFFSET_FROM_EXTRUDER 40 // X offset: -left +right [of the nozzle]
Y_PROBE_OFFSET_FROM_EXTRUDER 0 // Y offset: -front +behind [the nozzle]