I use one of these as my main live fire shot timer. I think they normally run about $120.
http://amzn.to/2kL52lA
http://amzn.to/2kL52lA
Here's a trick I've learned to make my timer last longer........just don't practice! LOL
Got one for $108+shipping from Shooters Connection back in August. Fist and only timer thus far, but I'm liking it.