APU finding engine parts for Diamond Power systems unit stuck with

I have gotten stuck with one of the Diamond Powers Systems APUs. I can't get engine parts for it with out a Serial number from a Z482 Kubota engine on a carrier unit that the Diamond is a copy of. The copy is a JD 500-C .
Any have one of the carrier units or have any advice for me? I'm only using it to generate power for my rig. I saw an old thread but it didn't get me there.

Thanks in advance.