What Would Be A Balanced Eldritch Invocation That Involves Blindsight?

I’ve been trying to homebrew an Eldritch Invocation that grants the Warlock blindsight, but I’m not sure how far this blindsight should extend. I initially thought to compare it to the pre-existing invocation Devil’s Sight, which grants 120 feet of darkvision through magical and non-magical darkness, but blindsight is (obviously) far superior to darkvision, so I deserted that comparison. Any suggestions for how far the blindsight should extend would be greatly appreciated.

I was hoping to make this blindsight Eldritch Invocation have no Warlock level or Pact prerequisites, but I would be willing to add a level prerequisite if it’s absolutely necessary.