The flight tank is no longer supplied by Aerotech and Catalina Cylinders typically does not sell direct to consumer. Thankfully I stumbled across a direct replacement. They are available from racing CO2 shift systems. The best prices I have been able to find are from Jegs and Autometer.
https://www.jegs.com/i/JEGS/555/60205/10002/-1
The above bottle requires that you remove the valve.
https://www.autometer.com/co2-bottle-only-no-valve-dot-nhra-approved-10-ounce-capacity.html
The Autometer comes without the valve to save you a step. Don’t forget to do a through cleaning. It will be a multistep process, acetone, 99% percent isopropanol, then finish up with chlorinated brake cleaner, let dry. Use a UV light to look for the telltale petroleum green glow as it will fluoresce, If you see any, then reclean.
Not including the ground support you could have the making of a functional hybrid 54mm motor for approx 250.00 with the forward closure, internal parts, connectors, and injector plate( which will require machining). Of course you will also need the 54mm case and aft closure, which you should already have. Used is preferred in case of failures.
Patrick Carroll 