I've found a digitising probe that is on eBay and have asked the manufacturer if he thinks it's compatible with the Nomad 883 pro. His response was;
I've looked general description of this machine, photos, bit of spec. You should be able to use such sensor, at least I've seen this machine has built-in sensor for the length of the instrument. So, technically it should be possible.
Practically, I don't have schematics or description of its connectors to see if there is spare input port which could be used for this probe or it can be connected to the same input with tool length sensor.
From other hand, I see that the code G43 is "Accepted but ignored" - so, it is not clear how they implemented tool length compensation.
I would strongly advise you to ask the manufacturer about ability to work with probe, if they have any support for probing in software or maybe ability to write some scripts/code to control it - like G38.2 move and sens commands in mach3.
Unfortunately, I cannot help you better."
Does anyone have the technical expertise to tell me if this will be compatible and if so what other software I may need to enable the digitiser to map irregular shapes?