There’s no “one size fits all” solution, especially with stethoscopes. But that also goes for other equipment such as assisted listening devices that can be even more expensive. So do your best to agree a trial period with the supplier. This means you can get a full refund if you return the equipment in time,though delivery costs may not be included.
If you’re buying a stethoscope, try to have a trial period of at least a month. You may need to try several configurations and to try it out with real people. Probably friends and family but patients with audible signs if you have the chance. You may need an appointment with your audiologist to try adjusting programmes on your hearing aids or implants too. If there’s much of a waiting list, you may need to arrange the appointment and trial period ahead of time, so they coincide. And you may need time to meet up with another deaf/hard of hearing health professional with experience to help you set everything up.
And don’t forget to have your Access to Work or Disabled Students’ Allowance assessment before buying anything. AtW and DSA won’t pay out in retrospect.