The distributor I found for the air cylinders has the cylinders we'd need for just $33.20 including shipping (!) or $28.30 for 10. Frightprops cyclinders are $35.81 plus shipping. Of course, the benefit to FP is its in inches, probably ships faster, and everything I've heard about his customer service is top-notch.
"but his blood will I require at the watchman’s hand." - Ezekiel 33:4