if he already carries an ASP, he should consider adding the ASP window breaking cap.
while it might be possible to break auto glass with a traditional ASP using the baton part, it's obviously not the right tool for the job. you'll look like an idiot if it takes several strikes before it works.
if he's wearing it on his belt, he could consider the surefire 6PX tactical. not as expensive or modular as some of the other surefires, it's simple and bright.
and it fits in the surefire v70 speed holster