When I was a traveler, I worked with a nurse who was hearing impaired. She was using an electronic STETHOSCOPE which appeared to suit her needs beautifully. Perhaps you should check out this avenue. Your instructors may want to ensure that YOU not an instrument can determine patient values. An electronic scope would, in my opinion, allow you to do a multitude of tasks, auscultate lungs and hearts, as well as take BPs.
I have always put my money in my tools of my trade, a good stethoscope and a great pair of shoes.
Good Luck!!
HemoStat