UPDATE: turns out it's really hard to get the desk and chair the exact right height for both sitting and standing, so I went with a tall stool:
And coupled it with a keyboard/mouse tray:
two together were roughly $300, and I really like being able to adjust
the keyboard height - just mixing it up a big seems to help with RSI
since you can change the muscles a bit.
So I was about to raise my desk up to try a standing desk configuration, when it occurred to me I should first get a chair or stool that high so I can work either way (I do *not* want to be raising/lowering my desk).
I'm fairly tall (6-2), and did the simple math that to raise my desk from sitting elbow height now (29") to standing elbow height (47") would mean raising everything 18".
What does that mean for my stool? Well it is currently at 22", so it would mean raising it to 40". But despite all I've been reading about standing desks for a few years, I can't find a stool that high anywhere so far.
In case anyone else is going through the same thing, here are a few that get pretty close:
Amazon sells this one that goes to 36" - the highest I've found so far, and only $120:
Global Industrial has this one that goes to 34.5 inches, fancier and runs $250:
Sit Better has this one that goes to 34", runs $205 and looks pretty nice: