Hello Martijn,
As a FroggEye suggester... the best option will be to create a custom macro and one thing you can take benefit of is the context macro of Marketing that is passed to the Newsletter as a parameter:
{% OnlineMarketingContext.CurrentContact.ContactID %}
So you can simply use this in your custom macro and depending on the
ContactID you will be able to get all info about the contact that you need.
Best regards,
Martin Danko