Petition
If your fundraiser is socially oriented and you would like to start a petition for your cause, there are a number of platforms where you can do so. You can then refer to your Steunactie in the text of the petition (include the campaign page link!) so that visitors can not only sign the petition but also have the opportunity to support the cause with a donation.
https://www.degoedezaak.org/petitie-starten/
https://secure.avaaz.org/page/en