Call the company on the phone to order. I almost always do this if I've never ordered before. If their phone number and STREET address (not PO Box) is not somewhere on the site, they don't get my business.
This isn't a product I'd order. I don't see how simulating an asthma attack will make my lungs transfer more oxygen while I'm mountain biking. My diaphragm works fine, thank you.
That said, if he wants to order it, I'd say call 'em up. The USPS money order isn't a bad idea, of course.