Buy the tall one and get a saw?

I would try Bowery below Houston. There are several chair stores there which have navy chair knock-off styles like this stool. Good luck.

How short is the short one? Probably 24" and the too tall one is probably 30 or 31". Which are pretty standard.
http://www.urbanmode.com/counterandbarstoolsDetail.asp?ID=421

24":
http://www.homedecorators.com/detail.php?parentid=2478600&aid=froogle&CAWELAID=39896475

25": http://www.barstools.com/counter-height-stools/metal/sirenaluminumcounterstool.cfm

So what you need at this point is an adjustable one, which you won't find in that style. Here is one:
http://www.homeofficesolutions.com/product-exec/product_id/34/pn/Covey_Model_Six_Stool

"Seat adjusts from 23" to 28" to accomodate any height."

Here's a close-up of the part that spins around and the feet:
http://www.gabrielross.com/jeff-covey-model-stool-aluminum-seat-p-1512.html

Check also office supply places and look at regular adjustable stools. That way everyone can have their own height and be comfortable!

there are many varieties of emeco knock-off stools like this, but in all, there are bar-height (30in) and counter-height (24in) stools. nothing in between in a non-adjustable model (of course, there will be variation in each style, but...). it seems weird that one of the two won't work... is the counter really that short? how about some jacobsen-like stools -- the chrome legs would be easier to saw.

Thanks, everyone. I'm going to check out the Bowery chair stores this weekend. (And yes, the counter is a really weird height. We actually brought the 24" and 30" styles home to try them, and neither worked.)