Where can I buy a gas lift for a swivel chair?

Hi there:

Is it possible to buy a spare gas lift for a staples chair? They shipped me a new chair without one and are going to ship me an entire new chair instead of just the part! And they are not going to pick it up because it is not cost effective for them.

Here is the link to the chair:
http://www.staples.com/Staples-Cushing-Luxura-Managers-Chair/product_689451?storeId=10001&jspStoreDir=Staples&cmSearchKeyword=Staples%AE+Cushing+Luxura%99+Manager%27s+Chair+&fromUrl=home&langId=-1&catalogId=10051&cmArea=SEARCH&ddkey=StaplesSearch

-Soumyaroop