Per Brian's (BGENTRY's) mention of favoring a larger stone (for SiC), another inexpensive alternative is ACE Hardware's 8" x 2" x 1" stone in SiC (double-sided), for around $10 - $12 or so. ACE's stones seem to be very good quality for the little money invested. Brian is right, in mentioning I often favor a slightly smaller stone (6" or less), largely due to the method by which I favor using them in-hand (though I'm occasionally even doing this with 8" stones now). For the simple, relatively small & thin blades on the folding knives mentioned (Buck, Case) a 6" stone is plenty big enough to grind those simples steels very quickly. In addition to the two Norton Economy stones I've purchased, I have the larger ACE 8" stone in SiC, and also their portable/pocket-size stones in 4" (double-sided) & 3" ('Fine' single-sided), and they've all impressed me. The 4" stone is especially portable & handy, in my uses.
My larger point being, most any of the current generation of SiC stones from Norton, ACE and others seem to perform very well. That's more an attribute of, and a compliment to, the abrasive type itself and less about the size of the stone or the maker. In other words, it's unlikely you'll find a SiC stone that doesn't perform well for most uses, no matter what size is used or where you buy it. It's very hard to go wrong with them, and I've not yet found a spoiler in the 7 SiC stones I've accumulated (which is sort of why I accumulated that many, just out of intellectual curiosity in the abrasive type; I was LOOKING to find some significant differences or inconsistency in performance, but haven't yet found it).
David