I couldn't find "Cambridge N99" masks on Amazon.com.

Do note: If the mask has ear loops it is almost certainly not an N95 or better mask. It likely won't protect the wearer, but is fine for protecting others - so long as it doesn't have expiratory valves.

And huge thanks to Famdoc for pointing out the danger of expiratory (exhalation) valves. They should be taken off the market until the pandemic is history.