Hi, I just could not understand if you need a Magento or a Drupal developer. If it really is for Drupal and custom payment gateway, I'm in. For example, I had just finished this: https://www.freelancer.com/jobs/project-9990443/
Presenting myself, my name is Marcelo and I'm from Brazil. I am a CS graduated with more than 17 years experience in IT market, and +8 years experience with Drupal. I have some good works at my portfolio, and other minor websites to send you links if interested. I'm with 100% conclusion rate and positive feedbacks here at Freelancer.com and I pretend to keep that.
If interested, call me on chat or award this bid!
Regards,
Marcelo.
--