Peppol Directory are similar to phonebooks.
to find your customer or supplier's PEPPOL id
it is best you have their UEN.
for Singapore Company you can use IMDA's PEPPOL directory.
For International Company you will need to use the Global directory.
Notes about using global directory, if you do not have the UEN , you will need to include more search terms.
in this case just searching for company name yield 338 results.
by including the Country and zip code, the information is narrowed down.