The 624CF has been really hard to find ever since the main manufacturing plant suffered a major hit from a natural disaster a while back. I just talked to a rep who claims dealers will have them back in stock by the end of the month...I have my fingers crossed.
As an alternative you could get the Sirui t-1205x 5. A little more $ but you get greater stability and overall max height. It also is slighly more compact and the exact same weight as the 624cf. Mine has worked flawlessly.