We're looking for someone who's capable of integrating the known dutch payment system called Ideal. We currently use http://pay.nl but sadly their api is only in dutch. I don't mind translating this the best I can. 

https://www.pay.nl/webshops/plugins <- their api

Why dont you use payssion from the marketplace? They offer alot of payment methods also ideal, for only $25. Which is probably way cheaper than this custom script.