Does anyone know of a reputable online second opinion mri reading resource? (just so many ranging from $100-$300 per re reading)

Not really: You could ask the doctor who ordered your MRI to show the images to another radiologist. This would, of course, be an informal review that would not generate a separate report but would still provide a second opinion. Radiologists are frequently asked to review imaging studies that were formally interpreted by someone else and often do so for free. Any formal "re-read " will likely cost you.