Where to rent 4k Blu-Ray Discs Online?

Red Box? Pretty sure they still do, but believe you order them on-line and pick-up at a local ‘box’.

bkeske.....thanks for the suggestion.
However, I'm looking for a service that will mail me the discs like Netflix does and that I can also return the discs by mail.

Got it. Seems that’s how Netfix started, yet, these services seem practically ‘dead’ today. I’ve pretty much resorted to streaming for everything today, but it’s rare to spend money either renting or purchasing content these days. With a Roku (or similar), I have practically anything I want at my fingertips. Dropped cable years ago. 

Interesting, it really doesn’t seem that long ago when I used to to get movies at the VCR tape rental store regularly. I sold my nice Sony VCR to my postal carrier cheap, after she inquired while chatting about delivering a bunch of new vinyl to me. She was thrilled. I guess she had many VCR tapes with children content for her kids.