Not sure exactly what you can look for in the portfolio other than high quality and similar style models to what you need. Speaking only for myself from an artistic perspective, the accuracy of the model will depend heavily on the quality of the references you can provide. For instance, in photogrammetry, you would need to take dozens of reference photos from every angle of an object to get the best point cloud representation of a real-world object in 3d. With hand-modeled geometry, most artists need at least 3 good reference images to get an accurate representation. Top, side, and front views are a must. To get an accurate clone of an image, sometimes more than those 3 angles are required, and then some close-up shots for more detailed areas would also be helpful. Good luck, I'm sure you will find someone. There are many, many talented artists here.