Hi Josh, our team at Salytics does this for clients all the time. We are a Gold Digital Services Partner of Marketo and most of our team is Marketo Certified Solutions Architects and the rest are Marketo Certified Experts. Feel free to connect with me email@example.com and we can discuss your needs.
You could go direct to Email Monks, they are excellent, and fast. They will code from a design layout or if its amends they can do that and ensure all the relevant responsive / outlook code all work.