The FAA granted PRNAV approval to any IFR approved GPS installation (which is sensible because e.g. GPS approaches are RNP 0.3 whereas PRNAV is RNP 1.0) but this is valid only in US airspace.
The only GA GPSs which are approvable for PRNAV in Europe are GNSx30, GNSx30W, G500, G1000 etc i.e. only the ~ year 2000 onwards avionics.
PRNAV approval is an EASA Major Mod. I don't know what the current FAA (N-reg) approval route is; the NY IFU stopped doing avionics 337s several years ago.
There is a curious footnote on page 2 of that PDF, saying that GA was not surveyed. I wonder if the powers to be are planning on exemptions? The majority of bizjets are not PRNAV approved, for example.