The Voldyne 5000 Volumetric Exerciser is available through Amazon as well as several others at a very reasonable price.
There are others available from Amazon and the price is right.
Cardinal Health AirLife Volumetric Incentive Spirometer has 5 star rating for $8.59 plus shipping.
And as already mentioned, most of the major pharmacies carry Incentive Spirometer device in their stores.
and Heart/Cardiovascular Disease. "She Stood in the Storm & When the Wind Did Not Blow Her Away, She Adjusted Her Sails."