Try emailing Sabien Canton. I hope this address still works: firstname.lastname@example.org (let me know if it doesn’t)
I am a Dutch harpist, but I don’t live in The Netherlands right now. Sabien Canton doesn’t live in the city Amsterdam but she is very active within the Dutch harp scene and has a lot of contacts there (she is also a member of the editorial staff of the Dutch Harp Bulletin. She will certainly be able to refer you to someone from Amsterdam who teaches at your level.