I think currently the answer is No. I would suggest you to open a case with PTC support to open an enhancement request to provide it as a Standalone widget for previous versions.
Other option could be to copy the widget folder from the ThingWorx 7.4 exploded folder i.e. <ThingWorx_Tomcat_Home>\webapps\Thingworx\Common\thingworx\widgets\eventsrouter and use it to create your own widget for previous versions.
I know you would ask
Well, it brilliantly solves my issues when I wanted to route more widget's (or service's) outputs to one input parameter in one service. Which is not possible normally. I always made some workarounds (more services invoked by more buttons for an example a concat the output.). Events router let you define many inputs and their types and it has one output with trigger on change.
Needles to say this is a must have Widget.