How to create byte[] with size using reflections?

Introduction:
So, I'm using an API and I need to overwrite 2 100% identical functions, one returning byte[] and one returning short[]. To make sure I don't have to edit everything twice, I want to create a function returning the required one. But to achieve this I would need to create a byte[4096] or a short[4096] which cannot be casted to anything, so I thought about using reflections and check whether a byte[] or a short[] is required.
Problem:
I don't know how to create a fixed-sized byte[] using reflections, so I'm asking this right here.