Podcasts are just audio or listening scripts. If you go with actual shows, they'll be quite long but plenty of ESL websites publish shorter ESL student targeted podcasts.
Check
PodCards for some students podcasts
Medical English worksheets, teaching resources and free activities for healthcare professionals has a couple ESP medical audio downloads
Breaking News English Lessons: ESL Plans Teaching Current Events publishes audio with every news article
There are plenty of others, just search for ESL podcasts.
Just prescreen the audio files and make focus questions that go along with the script. Some of th sites may have those already prepared for you.
I do a show for teachers if you're interested
ESL Teacher Talk