ECU might still be OK since it was running when you shut it off. I'd just replace the VRR and battery, make sure of the correct voltage, and ride it to see if anything else is fried. Oh yeah, you might want to install a voltmeter on your bike somewhere where you can see it while riding. Very handy item.
DISCLAIMER: All observations made in this post are mine and based solely on my own anecdotal experiences, and may contain large doses of facetiousness. YMMV, of course. You are "on your own", and I take no responsibility if someone tries anything in this post and gets into trouble with the law, damages their person or property, or goes blind. Take everything you read or hear "anywhere" butt especially on the Web with a large dose of salt.