I have the Pocket Chamber, which also has a thing in it that whistles if you inhale too fast.   I think it's probably made by the same company.  But this company's excellent products don't seem to be too widely available.   No store in Austin Texas carries it, and I had to order it from the Internet, after some searching.   I originally got my old one from my doctor.  And since I couldn't get it from the local county charity medical program drug store chain, I had to pay for it out of pocket.  Luckily it cost only half the $40 or $50 that would have been the out of pocket cost of the one model that drug store does carry - and that's the main supermarket chain in Austin (HEB).  

What I most like about it is that it fits in my purse.  I don't know how anyone expects anyone, let alone a child or an athlete, to carry those great big thingies they most often sell.   Really, a toilet paper roll would make more sense.   Atleast the thing collapses!

Dora