Hi,
I had the same dilemma I like using the reader as I can just grab it out of a pocket and not worry about unlocking my phone etc, I don't sync my reader I just use it for alarms and a quick read, on the go.
I use my phone for syncing to LibreLink. The volume for the alarms are the same as the reader alerts etc, I tested this by setting a reminder for a few minutes ahead and waited to see how loud it was, it is not that loud.
But as said above you can put it in a glass, on top of a tin etc to make it louder. But I get around this in a different way, I put the reader under my pillow at night and the vibration and sound wakes me up.