http://www.drugs-test.nl/waar-kan-ik-drugs-laten-testen (Dutch site)
This is the link where all drug-testing facilities in Holland are located.
You can have almost any drug tested, except for mushrooms, cannabis, medication (some DMT derivatives can't be identified with mass spectrometry as well).
Hope this is the information you need. You can always send me a PM for questions about testing facilities or related things!
Cheers