[josephcsible]

There's a reason that you haven't found any open source licenses that already have such a clause: any license that did would violate the Open Source Definition. The best way to accomplish your goal is to license your code freely to everyone under the AGPLv3, and then sell exceptions to companies that refuse to use that license.

[bombcar]

This is the way to go, I feel, unless you have some other way of "guaranteeing" that the source becomes unencumbered when abandoned/the company fails.

Either way you're going to be better served by using existing licenses than trying to roll your own.