Nitecore and 4Sevens make really nice ones, both single and double chamber. I have a tube shaped Ti one from CountyComm.com. Less expensive with very little volume and weight. It hangs on my key ring. I suspect it is the Vargo, but I am not sure. Loud but very high pitch - if you work with old shooters it might not work as well. (-: The Fox 40 Micro that comes in the Ritter PSK is great and much less expensive if you can stand the storage volume, they are much larger.

Respectfully,

Jerry