You can also look for the 4x5 "bag mags" which were the forerunner to the grafmatic. They are only usable on the early graflex cameras so might be a little cheaper. Best of all they come with twelve septums rather than just the six in a grafmatic. They are thicker than the grafmatic septums but otherwise the same size (see the differences here: http://www.paulewins.com/blog/?page_id=52 ). Either type of septum can be found on ebay in replacement sets with a little patience and is usually cheaper than buying a compete grafmnatic or bag mag.
Whoa, now that's the kind of tip I like! I never thought of the old "mag bags", but I need twelve septums anyway and that sounds like the way to go. Thanks a bunch! JW