A sample of your blood or skin, which medical probably already has in the records from when they pulled you off Phelolu. Your species is new, so there'd be some trial and error involved in getting the limb to grow properly, but that's on the back end and you won't have to deal with any of it. When it's ready, there's a finicky but not risky surgical procedure to attach it, then you have a few weeks of re-learning how to use the arm.

[See? Easy. Cortana says it all like she's discussing logistics for a carpool.]