FRS Reverse Light Mod like the Nightrunner FRS
 

Anyone know where I can get this Reverse light mod? Or how to do it?

First, why would you want to do that? Having a strobe light for a reverse light is a really stupid idea.

Second, I'm pretty sure it'd be illegal in Commifornia.

Third, basically any normal tail light flasher kit could probably be wired up to work on a single reverse light. Just google "tail light flasher kit" and you'll be able to find what you need.